Earthquake

Global earthquake epicenters, 1963–1998

An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. The word earthquake is also widely used to indicate the source region itself. The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics). Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. The highest stress (and possible weakest zones) are most often found at the boundaries of the tectonic plates and hence these locations are where the majority of earthquakes occur. Events located at plate boundaries are called interplate earthquakes; the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes (see, for example, New Madrid Seismic Zone). Earthquakes related to plate tectonics are called tectonic earthquakes. Most earthquakes are tectonic, but they also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust. Seismic waves including some strong enough to be felt by humans can also be caused by explosions (chemical or nuclear), landslides, and collapse of old mine shafts, though these sources are not strictly earthquakes.

Characteristics

Large numbers of earthquakes occur on a daily basis on Earth, but the majority of them are detected only by seismometers and cause no damage .

Most earthquakes occur in narrow regions around plate boundaries down to depths of a few tens of kilometres where the crust is rigid enough to support the elastic strain. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. At subduction zones where plates descend into the mantle, earthquakes have been recorded to a depth of 600 km, although these deep earthquakes are caused by different mechanisms than the more common shallow events. Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle.

Large earthquakes can cause serious destruction and massive loss of life through a variety of agents of damage, including fault rupture, vibratory ground motion (i.e., shaking), inundation (e.g., tsunami, seiche, dam failure), various kinds of permanent ground failure (e.g. liquefaction, landslide), and fire or a release of hazardous materials. In a particular earthquake, any of these agents of damage can dominate, and historically each has caused major damage and great loss of life, but for most of the earthquakes shaking is the dominant and most widespread cause of damage. There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard.

Damage from the 1906 San Francisco earthquake. Section of collapsed freeway after the 1989 Loma Prieta earthquake.

Most large earthquakes are accompanied by other, smaller ones, that can occur either before or after the principal quake — these are known as foreshocks or aftershocks, respectively. While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. The power of an earthquake is distributed over a significant area, but in the case of large earthquakes, it can spread over the entire planet. Ground motions caused by very distant earthquakes are called teleseisms. The Rayleigh waves from the Sumatra-Andaman Earthquake of 2004 caused ground motion of over 1 cm even at the seismometers that were located far from it, although this displacement was abnormally large. Using such ground motion records from around the world it is possible to identify a point from which the earthquake's seismic waves appear to originate. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. The location on the surface directly above the hypocenter is known as the "epicenter". The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. Just as a large loudspeaker can produce a greater volume of sound than a smaller one, large faults are capable of higher magnitude earthquakes than smaller faults are.

Earthquakes that occur below sea level and have large vertical displacements can give rise to tsunamis, either as a direct result of the deformation of the sea bed due to the earthquake or as a result of submarine landslips or "slides" directly or indirectly triggered by it.

Earthquake Size

The first method of quantifying earthquakes was intensity scales. In the United States the Mercalli (or Modified Mercalli, MM) scale is commonly used, while Japan (shindo) and the EU (European Macroseismic Scale) each have their own scales. These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. The value 6 (normally denoted "VI") in the MM scale for example is:

Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No structural damage.

A Shakemap recorded by the Pacific Northwest Seismograph Network that shows the instrument recorded intensity of the shaking of the Nisqually earthquake on February 28, 2001. A Community Internet Intensity Map generated by the USGS that shows the intensity felt by humans by ZIP Code of the shaking of the Nisqually earthquake on February 28, 2001.

The problem with these scales is the measurement is subjective, often based on the worst damage in an area and influenced by local effects like site conditions that make it a poor measure for the relative size of different events in different places. For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. If you feel an earthquake in the US you can report the effects to the USGS.

The first attempt to qualitatively define one value to describe the size of earthquakes was the magnitude scale (the name being taking from similar formed scales used on the brightness of stars). In the 1930s, a California seismologist named Charles F. Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). It is obtained by measuring the maximum amplitude of a recording on a Wood-Anderson torsion seismometer (or one calibrated to it) at a distance of 600km from the earthquake. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). Each of these is scaled to gives values similar to the values given by the Richter scale. However as each is also based on the measurement of one part of the seismogram they do not measure the overall power of the source and can suffer from saturation at higher magnitude values (larger events fail to produce higher magnitude values).These scales are also empirical and as such there is no physical meaning to the values. They are still useful however as they can be rapidly calculated, there are catalogues of them dating back many years and are they are familiar to the public. Seismologists now favor a measure called the seismic moment, related to the concept of moment in physics, to measure the size of a seismic source. The seismic moment is calculated from seismograms but can also by obtained from geologic estimates of the size of the fault rupture and the displacement. The values of moments for different earthquakes ranges over several order of magnitude. As a result the moment magnitude (MW) scale was introduced by Hiroo Kanamori, which is comparable to the other magnitude scales but will not saturate at higher values.

Larger earthquakes occur less frequently than smaller earthquakes, the relationship being exponential, ie roughly ten times as many earthquakes larger than 4 occur in a particular time period than earthquakes larger than magnitude 5. For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:

  • an earthquake of 3.7 or larger every 1 year
  • an earthquake of 4.7 or larger every 10 years
  • an earthquake of 5.6 or larger every 100 years.

Causes

Most earthquakes are powered by the release of the elastic strain that accumulate over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. Where these plates meet stress accumulates. Eventually when enough stress accumulates, the plates move, causing an earthquake. Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. A rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (e.g. at certain geothermal power plants and at the Rocky Mountain Arsenal). Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. Finally, ground shaking can also result from the detonation of explosives. Thus scientists have been able to monitor, using the tools of seismology, nuclear weapons tests performed by governments that were not disclosing information about these tests along normal channels. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity.

Another type of movement of the Earth is observed by terrestrial spectroscopy. These oscillations of the earth are either due to the deformation of the Earth by tide caused by the Moon or the Sun, or other phenomena.

A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake storm, where one earthquake will trigger a series of earthquakes each triggered by the previous shifts on the fault lines, similar to aftershocks, but occurring years later.

Preparation for earthquakes

  • Emergency preparedness
  • Household seismic safety
  • Seismic retrofit
  • Earthquake prediction

Specific fault articles

  • Alpine Fault
  • Calaveras Fault
  • Hayward Fault Zone
  • North Anatolian Fault Zone
  • New Madrid Fault Zone
  • San Andreas Fault

Specific earthquake articles

  • Shaanxi Earthquake (1556). Deadliest known earthquake in history, estimated to have killed 830,000 in China.
  • Cascadia Earthquake (1700).
  • Kamchatka earthquakes (1737 and 1952).
  • Lisbon earthquake (1755).
  • New Madrid Earthquake (1811).
  • Fort Tejon Earthquake (1857).
  • Charleston earthquake (1886). Largest earthquake in the Southeast and killed 100.
  • San Francisco Earthquake (1906).
  • Great Kanto earthquake (1923). On the Japanese island of Honshu, killing over 140,000 in Tokyo and environs.
  • Kamchatka earthquakes (1952 and 1737).
  • Great Chilean Earthquake (1960). Biggest earthquake ever recorded, 9.5 on Moment magnitude scale.
  • Good Friday Earthquake (1964) Alaskan earthquake.
  • Ancash earthquake (1970). Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people.
  • Sylmar earthquake (1971). Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989.
  • Tangshan earthquake (1976). The most destructive earthquake of modern times. The official death toll was 255,000, but many experts believe that two or three times that number died.
  • Great Mexican Earthquake (1985). 8.1 on the Richter Scale, killed over 6,500 people (though it is believed as many as 30,000 may have died, due to missing people never reappearing.)
  • Whittier Narrows earthquake (1987).
  • Armenian earthquake (1988). Killed over 25,000.
  • Loma Prieta earthquake (1989). Severely affecting Santa Cruz, San Francisco and Oakland in California. Revealed necessity of accelerated seismic retrofit of road and bridge structures.
  • Northridge, California earthquake (1994). Damage showed seismic resistance deficiencies in modern low-rise apartment construction.
  • Great Hanshin earthquake (1995). Killed over 6,400 people in and around Kobe, Japan.
  • İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey.
  • Düzce earthquake (1999)
  • Chi-Chi earthquake (1999).
  • Nisqually Earthquake (2001).
  • Gujarat Earthquake (2001).
  • Dudley Earthquake (2002).
  • Bam Earthquake (2003).
  • Parkfield, California earthquake (2004). Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures.
  • Chuetsu Earthquake (2004).
  • Indian Ocean Earthquake (2004). One of the largest earthquakes ever recorded at 9.0. Epicenter off the coast of the Indonesian island Sumatra. Triggered a tsunami which caused nearly 300,000 deaths spanning several countries.
  • Sumatran Earthquake (2005).
  • Fukuoka earthquake (2005).
  • Kashmir earthquake (2005). Killed over 79,000 people. Many more at risk from the Kashmiri winter.
  • Lake Tanganyika earthquake (2005).

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A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake storm, where one earthquake will trigger a series of earthquakes each triggered by the previous shifts on the fault lines, similar to aftershocks, but occurring years later. The following are interesting but little known facts about Puerto Rico and its people:. These oscillations of the earth are either due to the deformation of the Earth by tide caused by the Moon or the Sun, or other phenomena. It is also home to more than 240 plants, 26 of which are endemic and 50 bird species, including one of the top 10 endangered birds in the world, the Puerto Rican Parrot. Another type of movement of the Earth is observed by terrestrial spectroscopy. It is home to the majority (13 of 16) of species of coquí. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity. The Caribbean National Forest, also known as El Yunque (the name of its highest peak), is a tropical rainforest located in the eastern region of the main island.

Thus scientists have been able to monitor, using the tools of seismology, nuclear weapons tests performed by governments that were not disclosing information about these tests along normal channels. The coquí is a small frog easily recognized by the sound from which it gets its name. Finally, ground shaking can also result from the detonation of explosives. The most recognizable endemic species and a symbol of Puerto Rican pride is the Coquí. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. The majority of these (234,33 and 12 repectively) are found in the main island. Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. As of 1998 [16], 239 plants, 13 birds and 39 amphibians/reptiles have been discovered that are endemic to the island of Puerto Rico or its smaller islands (Culebra, Vieques, Mona and Desecheo).

at certain geothermal power plants and at the Rocky Mountain Arsenal). On September 29, 2005 Major League Baseball announced that opening rounds of the newly formed World Baseball Classic, a 16-country tournament featuring top players, would be held in San Juan in March 2006. A rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (e.g. August 8, 2004 became a landmark date for Puerto Rico's national olympic team when the basketball team of Puerto Rico defeated the US basketball team nicknamed US Dream Team in Athens,Greece [15]. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. Puerto Rico has participated in the World Cup of Baseball winning 1 gold (1951), 4 silver and 4 bronze medals. Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported. and became the Washington Nationals.

Eventually when enough stress accumulates, the plates move, causing an earthquake. Puerto Rico has its own professional baseball leagues, though San Juan hosted the Montréal Expos for several series in 2002 and 2003 before they moved to Washington, D.C. Where these plates meet stress accumulates. Although boxing, basketball, and baseball are popular, traditionally baseball has been the most popular sport. The Earth is made up of tectonic plates driven by the heat in the Earth's mantle and core. Puerto Rican athletes have won 6 medals (1 silver, 5 bronze) in Olympic competition, the first one in 1948 by boxer Juan Evangelista Venegas. Most earthquakes are powered by the release of the elastic strain that accumulate over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory. Puerto Rico has an Olympic team in the Summer Olympics and the Winter Olympics, as well as international representation in many other sporting events including the Pan-American Games, the Central American Games, and the Caribbean World Series.

For example it has been calculated that the average recurrence for the United Kingdom can be described as follows:. By gender, the literacy rate is 93.9% for males and 94.4% for females. Larger earthquakes occur less frequently than smaller earthquakes, the relationship being exponential, ie roughly ten times as many earthquakes larger than 4 occur in a particular time period than earthquakes larger than magnitude 5. As of 2002, the literacy rate of the population was 94.1%. As a result the moment magnitude (MW) scale was introduced by Hiroo Kanamori, which is comparable to the other magnitude scales but will not saturate at higher values. Mendez which operates the Universidad del Turabo, Metropolitan University and Universidad del Este, the multi-campus Interamerican University, the Pontificial Catholic University and Sacred Heart University. The values of moments for different earthquakes ranges over several order of magnitude. The largest private university systems on the island are the Sistema Universitario Ana G.

The seismic moment is calculated from seismograms but can also by obtained from geologic estimates of the size of the fault rupture and the displacement. The two public universities in Puerto Rico are the multi-campus University of Puerto Rico and the Colegio Universitario de San Juan operated by the city of San Juan. Seismologists now favor a measure called the seismic moment, related to the concept of moment in physics, to measure the size of a seismic source. Public schools are run by the state while private schools are run by private institutions, predominantly the Roman Catholic Church. They are still useful however as they can be rapidly calculated, there are catalogues of them dating back many years and are they are familiar to the public. Students can attend either a public or a private school. However as each is also based on the measurement of one part of the seismogram they do not measure the overall power of the source and can suffer from saturation at higher magnitude values (larger events fail to produce higher magnitude values).These scales are also empirical and as such there is no physical meaning to the values. These are elementary, intermediate, high school and the university level.

Each of these is scaled to gives values similar to the values given by the Richter scale. Education in Puerto Rico is divided into four levels. Other more recent Magnitude measurements include: body wave magnitude (mb), surface wave magnitude (Ms) and duration magnitude (MD). The island's contestant was second-runner up in the 2005 Miss World pageant, and currently has the title of Miss World Caribbean. It is obtained by measuring the maximum amplitude of a recording on a Wood-Anderson torsion seismometer (or one calibrated to it) at a distance of 600km from the earthquake. Puerto Rican beauty queens have won the Miss Universe pageant 4 times (1970, 1985, 1993, 2001), and the Miss World pageant once (1975). This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (ML). Puerto Rico has its own representatives in beauty pageants including Miss World and Miss Universe.

Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. The unofficial national animal is the Coquí (Eleutherodactylus coqui). In the 1930s, a California seismologist named Charles F. The official national symbols of Puerto Rico are:. The first attempt to qualitatively define one value to describe the size of earthquakes was the magnitude scale (the name being taking from similar formed scales used on the brightness of stars). See also:Protestants in Puerto Rico.. If you feel an earthquake in the US you can report the effects to the USGS. Although Santeria (stronger and more organized in Cuba) is practiced by some, Palo mayombe (an African belief system of Bantu origin) finds more adherence among individuals who practice some form of African Traditional Religion.

For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. Kongo belief, known as Mayombe or Palo, has been around since the days of the arrival of enslaved Africans. The problem with these scales is the measurement is subjective, often based on the worst damage in an area and influenced by local effects like site conditions that make it a poor measure for the relative size of different events in different places. Taíno religious practices have to a degree been rediscovered/reinvented by a few handfuls of advocates. No structural damage. For example, the first non-Catholic church, Holy Trinity Anglican church in Ponce, now a parish of the Diocese of Puerto Rico of the Episcopal Church of the United States, was not allowed to ring its church bell until American troops marched through Ponce after landing at Guanica harbor on July 25, 1898. Damage is slight in poorly built buildings. Protestantism was repressed under the Spanish regime.

Trees and bushes shake. The Roman Catholic religion has been historically dominant and is the religion of the majority of Puerto Ricans (census: 70%), although the presence of Protestant, Latter-Day Saint (Mormon) and Jehovah's Witnesses denominations has increased under American sovereignty, making modern Puerto Rico an interconfessional country. Plaster in walls might crack. This was seen by many as a move by the pro-statehood governor to move the island closer to statehood, something that never came about under his two consecutive four-year terms. Furniture moves. Upon his election as governor in 1993, Governor Pedro Rosselló overturned the law and re-established English as an official language. Pictures fall off walls. The award is given annually to individuals and organizations worldwide for their defense and contribution to the growth of the Spanish language by Principe Felipe of Spain.

Objects fall from shelves. The signing of the law also brought the island acclaim, as the people of Puerto Rico won the prestigious Prince of Asturias Award in literature in 1991. People have trouble walking. While many applauded the governor's decision, mainly members of the parties supporting commonwealth-status and indepedence, statehood supporters saw it as a threat to their ideology. Everyone feels movement. Upon signing this law into effect, English had lost its status as an official second language. The value 6 (normally denoted "VI") in the MM scale for example is:. In 1991, Governor Rafael Hernández Colón signed a law declaring Spanish as the sole official language of the island's government.

These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. Even though a small minority use English as a main language the large majority of Puerto Ricans living in metropolitan areas are bilingual. In the United States the Mercalli (or Modified Mercalli, MM) scale is commonly used, while Japan (shindo) and the EU (European Macroseismic Scale) each have their own scales. As of 1996, an estimated 3,437,120 people used Spanish as their primary language and 82,000 spoke English. The first method of quantifying earthquakes was intensity scales. Spanish is the primary language in government; English is taught as a foreign language in schools. Earthquakes that occur below sea level and have large vertical displacements can give rise to tsunamis, either as a direct result of the deformation of the sea bed due to the earthquake or as a result of submarine landslips or "slides" directly or indirectly triggered by it. The official languages of the island are Spanish and English.

Just as a large loudspeaker can produce a greater volume of sound than a smaller one, large faults are capable of higher magnitude earthquakes than smaller faults are. Also 95% of the population consider themselves of Puerto Rican descent (regardless of race or skin color), making Puerto Rico one of the most culturally homogenous societies in the world. The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. These #s demonstrate that racial terms are relative, not absolute, and highlight the potential for confusion when they are used in a definitive and distinct way. The location on the surface directly above the hypocenter is known as the "epicenter". The breakdown is as follows: 80.5% described themselves as "white"; 8% described themselves as "Black"; and only 0.4% described themselves as "Native American" [14]. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. 95.8% answered with only one choice.

Using such ground motion records from around the world it is possible to identify a point from which the earthquake's seismic waves appear to originate. During the 2000 US Census Puerto Ricans were asked to identify which racial category with which they personally identify. The Rayleigh waves from the Sumatra-Andaman Earthquake of 2004 caused ground motion of over 1 cm even at the seismometers that were located far from it, although this displacement was abnormally large. Emigration continues at the present time, and this, combined with Puerto Rico's greatly lowered birth rate, suggests that the island's population will age rapidly and start to decline sometime within the next couple of decades. Ground motions caused by very distant earthquakes are called teleseisms. This continued even as Puerto Rico's economy improved and the birth rate declined. The power of an earthquake is distributed over a significant area, but in the case of large earthquakes, it can spread over the entire planet. Starting in the Post-WWII period, due to poverty, cheap air fare, and promotion by the island government, waves of Puerto Ricans moved to the United States, particularly New York City and Hartford, Connecticut.

While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. Emigration has been a major part of Puerto Rico's recent history as well. Most large earthquakes are accompanied by other, smaller ones, that can occur either before or after the principal quake — these are known as foreshocks or aftershocks, respectively. The variety of surnames which exist in Puerto Rico suggests widespread immigration to the island from many regions. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard. Argentines, Cubans, Dominicans, Colombians, Panamanians and Venezuelans can also be accounted for as settlers. There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. More recently Puerto Rico has become the permanent home of over 100,000 legal residents who immigrated from not only Spain, but from Latin America as well.

In a particular earthquake, any of these agents of damage can dominate, and historically each has caused major damage and great loss of life, but for most of the earthquakes shaking is the dominant and most widespread cause of damage. Other settlers have included Irish, Scots, Germans, and many others who were granted land from Spain during the Cedula de Gracias of 1815, which allowed European Catholics to settle in the island with a certain amount of free land. liquefaction, landslide), and fire or a release of hazardous materials. During the 1800s, hundreds of Corsican, French, Lebanese, and Portuguese, along with a large numbers of immigrants from the Canary Islands and numerous Spanish loyalists from Spain's former colonies in South America, arrived in Puerto Rico. Large earthquakes can cause serious destruction and massive loss of life through a variety of agents of damage, including fault rupture, vibratory ground motion (i.e., shaking), inundation (e.g., tsunami, seiche, dam failure), various kinds of permanent ground failure (e.g. This indicates that 59% of the population of Belen has an Amerindian mother somewhere down the ancestral line, while less than 5% of them have a male Amerindian ancestor. Some deep earthquakes may be due to the transition of olivine to spinel, which is more stable in the deep mantle. In Belen, Brazil, for example, mtDNA analysis identifies 59% of the contemporary population as Amerindian, while Y-chromosome analysis identifies less than 5% as Amerindian.

At subduction zones where plates descend into the mantle, earthquakes have been recorded to a depth of 600 km, although these deep earthquakes are caused by different mechanisms than the more common shallow events. Similar studies in other countries have yielded similar results. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. These results cast doubt on the notion that the Tainos disappeared from Puerto Rico by the end of the sixteenth century. Most earthquakes occur in narrow regions around plate boundaries down to depths of a few tens of kilometres where the crust is rigid enough to support the elastic strain. The results of the analysis of approximately 300 samples identify 62% as Amerindian, 30% as African blacks and 8% Caucasian. Large numbers of earthquakes occur on a daily basis on Earth, but the majority of them are detected only by seismometers and cause no damage . In August, 1999 a researcher at the University of Puerto Rico at Mayagüez received a grant from the National Science Foundation to determine the continental origin of the mtDNA of Puerto Ricans through the analysis of a representative sample.

. Puerto Rico has sometimes been said to have a European (Spanish) descent majority, an extinct Amerindian population, persons of mixed ancestry, Africans, and a small Asian minority. Seismic waves including some strong enough to be felt by humans can also be caused by explosions (chemical or nuclear), landslides, and collapse of old mine shafts, though these sources are not strictly earthquakes. Since 1952, the gap between Puerto Rico's per capita income and US national levels has essentially remained unchanged---one third the US national average and roughly half that of the poorest state. Most earthquakes are tectonic, but they also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust. Census Bureau’s Current Population Survey, 2002 to 2004 Annual Social and Economic Supplements [13]. Earthquakes related to plate tectonics are called tectonic earthquakes. By comparison, the poorest State of the Union, Mississippi, had a median level of $21,587, according to the U.S.

Events located at plate boundaries are called interplate earthquakes; the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes (see, for example, New Madrid Seismic Zone). In that survey, Puerto Ricans have a 48.2% poverty rate. The highest stress (and possible weakest zones) are most often found at the boundaries of the tectonic plates and hence these locations are where the majority of earthquakes occur. Puerto Ricans had a per capita GDP estimate of $17,700 for 2004 [11] , which demonstrates a growth over the $14,412 level measured in the 2002 Current Population Survey by the Puerto Rican Legal Defense and Education Fund [12]. Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. An increase in hotel registrations, which has been observed since 1998, and the construction of new hotels and the Puerto Rico Convention Center are indicators of the current strength of the tourism industry. The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics). Nearly a third of these are cruise ship passengers.

The word earthquake is also widely used to indicate the source region itself. In 1999 an estimated 5 million tourists visited the island, most from the United States. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. Tourism is an important component of the Puerto Rican economy supplying an approximate $1.8 billion. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. trade laws and restrictions. An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. Puerto Rico is subject to U.S.

Lake Tanganyika earthquake (2005). and foreign owned factories have moved to lower wage countries in Latin America and Asia. Many more at risk from the Kashmiri winter. In recent years, some U.S. Killed over 79,000 people. minimum wage legislation. Kashmir earthquake (2005). government, today local industries must compete with those in more economically depressed parts of the world where wages are not subject to U.S.

Fukuoka earthquake (2005). Once the beneficiary of special tax treatment from the U.S. Sumatran Earthquake (2005). The economic conditions in Puerto Rico have improved dramatically since the Great Depression due to external investment in capital-intensive industry such as petrochemicals, pharmaceuticals, and technology. Triggered a tsunami which caused nearly 300,000 deaths spanning several countries. Thus manufacturing replaced agriculture as the main industry. Epicenter off the coast of the Indonesian island Sumatra. In the late 1940's a series of projects called Operation Bootstrap encouraged, using tax exemptions, the establishment of factories.

One of the largest earthquakes ever recorded at 9.0. In the early 1900's the greatest contributor to Puerto Rico's economy was agriculture, its main crop being sugar. Indian Ocean Earthquake (2004).
. Chuetsu Earthquake (2004). The last municipality was Florida, founded in 1971 [10]. Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures. Only six municipalities were founded in the 20th century.

Parkfield, California earthquake (2004). 30 municipalities were established in the 18th century and 34 more were established in the 19th century. Bam Earthquake (2003). The 18th and 19th century saw an increase in settlement in Puerto Rico. Dudley Earthquake (2002). These were Arecibo (1614), Aguada (1692) and Ponce (1692). Gujarat Earthquake (2001). Three more municipalities were established in the 17th century.

Nisqually Earthquake (2001). In the 16th century two more municipalities were established, Coamo (1570) and San Germán (1570). Chi-Chi earthquake (1999). The first municipality (previously called "town") of Puerto Rico, San Juan, was founded in 1521. Düzce earthquake (1999). Each municipality has a mayor and a municipal legislature elected for a 4 year term. İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey. Municipalities are further subdivided into barrios, and those into sectors.

Killed over 6,400 people in and around Kobe, Japan. Government, but there are 78 municipalities at the second level (Mona Island is not a municipality, but part of the municipality of Mayagüez). Great Hanshin earthquake (1995). As an unincorporated territory of the United States (as recently defined by the White House), Puerto Rico does not have any first-order administrative divisions as defined by the U.S. Damage showed seismic resistance deficiencies in modern low-rise apartment construction. Also rejects any colonial or territorial status as a status option and vows to keep working for the enhanced commonwealth status that was approved by the PPD in 1998 which included:. Northridge, California earthquake (1994). It also stated a compromise to challenge the task force report and validate the current status in all international forums including the United Nations.

Revealed necessity of accelerated seismic retrofit of road and bridge structures. The historic resolution denounces the task force as a political fraud that represents a threat to democracy and is in violation of the basic agreements held between the people of Puerto Rico and the United States since 1952[8][9]. Severely affecting Santa Cruz, San Francisco and Oakland in California. On January 4, 2006, Governor Anibal Acevedo Vilá announced the steps that he and the governing Popular Democratic Party will take in the following months. Loma Prieta earthquake (1989). The governor of Puerto Rico promised to challenge the task force report. Killed over 25,000. Constitution regarding territories.

Armenian earthquake (1988). According to a report by the President’s Task Force on Puerto Rico’s Status, released in December 2005, it is not possible “to bind future Congresses to any particular arrangement for Puerto Rico as a Commonwealth.” This determination was based on articles in the U.S. Whittier Narrows earthquake (1987). Most people advocate that the status of Commonwealth has been, and continues to be, a temporary solution. 8.1 on the Richter Scale, killed over 6,500 people (though it is believed as many as 30,000 may have died, due to missing people never reappearing.). House Committee on Resources stated that Puerto Rico’s current status “does not meet the criteria for any of the options for full self government.” The House Committee concluded that Puerto Rico is still an unincorporated territory of the United States under the territorial clause, that the establishment of local self-government with the consent of the people can be unilaterally revoked by Congress, and that Congress can also withdraw at any time the American citizenship now enjoyed by the residents of Puerto Rico as long as it achieves a legitimate Federal purpose, in a manner reasonably related to that purpose. Great Mexican Earthquake (1985). In fact, in a 1996 report on a Puerto Rico status political bill, the U.S.

The official death toll was 255,000, but many experts believe that two or three times that number died. The General Assembly did not apply its list of criteria to Puerto Rico for determining whether or not self-governing status had been achieved. The most destructive earthquake of modern times. For a territory to be deemed self-governing, the United Nations require:. Tangshan earthquake (1976). This resolution has not been revoked by the UN even though the political status is still debated in many international forums. Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989. The resolution garnered a favorable vote of fewer than 40% of the General Assembly, with over 60% abstaining or voting against it (20 to 16, with 18 abstentions).

Sylmar earthquake (1971). On November 27, 1953, shortly after establishment of the Commonwealth, the General Assembly of the UN approved Resolution 748, removing PR’s classification as a non-self-governing territory under article 73(e) of the Charter of the United Nations. Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people. The United Nations has intervened in the past to evaluate the legitimacy of Puerto Rico's political status, to ensure that the island's government structure complies with the standards of self-government that constitute the basic tenets of the United Nations Charter, its covenants, and its principles of international law. Ancash earthquake (1970). This is a very common and accepted international status given to all dependent territories, also called dependent "states" by the United Nations. Good Friday Earthquake (1964) Alaskan earthquake. Although Puerto Rico is, politically speaking, an unincorporated territory of the United States classified as a Commonwealth, Puerto Ricans and people from other nations refer to Puerto Rico as a país, the Spanish word for country.

Biggest earthquake ever recorded, 9.5 on Moment magnitude scale. Bush,suggested that a Federally sanctioned plebiscite provided by Congress should take place in Puerto Rico during 2006 to decide the island's political future. Great Chilean Earthquake (1960). His comments were made after the Presidential Task Force Report,composed of high-level officials from major federal departments appointed by President George W. Kamchatka earthquakes (1952 and 1737). He also said to a local newspaper that he thinks Puerto Rico should become a sovereign state (in Spanish). On the Japanese island of Honshu, killing over 140,000 in Tokyo and environs. On December 29, 2005, William Miranda Marin, mayor of the municipality of Caguas, urged Puerto Rican governor Anibal Acevedo Vila to sue the United States for $100,000,000,000, based on what he deemed as "damages suffered by the country" as a consequence of the status given to Puerto Rico in 1952 as a self-governing commonwealth of the United States.

Great Kanto earthquake (1923). Puerto Rico also is not included in the Current Population Surveys that the Census Bureau conducts to update its decennial census. San Francisco Earthquake (1906). citizens. Largest earthquake in the Southeast and killed 100. population count at all, although all Puerto Ricans are statutory U.S. Charleston earthquake (1886). Puerto Ricans living on the island are not counted among the Hispanics residing in the U.S.; in fact, they are not included in the U.S.

Fort Tejon Earthquake (1857). The other political parties tend to resist and voice their concerns over the legitimacy of the process.Ultimately, every vote fails as either non-binding upon United States Congress or because viable and appropriate status options have been excluded from the ballot. New Madrid Earthquake (1811). Because past processes for self-determination in Puerto Rico have not had Congressional support, the political parties in power have manipulated ballot options to favor the alternative of their predilection. Lisbon earthquake (1755). The winning choice was thus "none of the above.". Kamchatka earthquakes (1737 and 1952). The pro-commonwealth party, unwilling to favor commonwealth status if subject to the plenary powers of Congress and entailing a type of statutory American citizenship revocable at the will of Congress, campaigned for the fifth choice, which obtained 50.3% of the vote, as compared to 46.5% for statehood, 2.5% for independence, 0.3% for the type of free association presented in the ballot, and a 0.1% percent for commonwealth as defined by the legislature.

Cascadia Earthquake (1700). In the plebiscite, the commonwealth status was depicted, as subject to the plenary powers of Congress under the territorial clause, a depiction shared by Bill Clinton, the president at the time, as well as his predecessor, with a revocable US citizenship. Deadliest known earthquake in history, estimated to have killed 830,000 in China. Provision was also made for a fifth choice: "none of the above," the rejection of all such status options. Shaanxi Earthquake (1556). Subsequently, a 1998 plebiscite presented a choice among statehood and three other status formula defined by the pro-statehood legislative majority: commonwealth status, independence, and a form of free association under a treaty with the United States. San Andreas Fault. In a 1993 plebiscite, in which Congress played a more substantial role, the commonwealth status option on PR’s status received 48% of the vote, with 46% voting for statehood, 4% for independence, and a voter turnout of 73% of the voting population.

New Madrid Fault Zone. Following the plebiscite, efforts in the 1970s to enact legislation to address the status issue died in Congressional committees. North Anatolian Fault Zone. Puerto Rican leaders had lobbied for such an opportunity repeatedly, in 1898, 1912, 1914, 1919, 1923, 1929, 1932, 1939, 1943, 1944, 1948, 1956, and 1960. Hayward Fault Zone. This constituted the first plebiscite by the Legislature for a choice on three status options. Calaveras Fault. In 1967, the Legislative Assembly tested political interests of the Puerto Rican people by passing a plebiscite Act that allowed a vote on the status of Puerto Rico.

Alpine Fault. state, and the Puerto Rican Independence Party (PIP) seeks national independence. Earthquake prediction. The Popular Democratic Party (PPD) seeks to maintain or improve the current status, the New Progressive Party (PNP) seeks to fully incorporate Puerto Rico as a U.S. Seismic retrofit. A Commonwealth associated to the US since 1952, Puerto Rico today is torn by profound ideological rifts, as represented by its political parties, which stand for the current relationship or the two distinct future political scenarios: the status quo, statehood, and independence. Household seismic safety. For the past fifty years, a single issue has dominated Puerto Rican politics: its political status vis-à-vis the United States.

Emergency preparedness. citizens, Puerto Ricans are subject to military service and most federal laws. an earthquake of 5.6 or larger every 100 years. As statutory U.S. an earthquake of 4.7 or larger every 10 years. Also, they have limited access to several key federal programs. an earthquake of 3.7 or larger every 1 year. Further, island residents pay social security taxes and other federal taxes.

Although they pay hefty local taxes, island residents are not subject to federal income taxation, as a result of a US Supreme Court Decision that the United States treaty that acquired Puerto Rico from Spain superseded the United States Constitution, so that the United States citizens of Puerto Rico are not subject to the Revenue Clause of the United States Constitution. Residents of the island do not pay federal income tax on income from island sources, although they pay federal payroll taxes, which have a particularly heavy impact on Puerto Rico's relatively low-income workers. Congress acting as a delegate of the people of Puerto Rico. A non-voting Resident Commissioner is elected by the residents of Puerto Rico to the U.S.

Presidential elections, although a political party can have state-like voting delegations to the nominating conventions of both major national parties. Electoral College, and therefore Puerto Rican citizens do not participate in the U.S. Congress; neither does it have any electors in the U.S. Puerto Rico does not have voting representation in the U.S.

Under the 1952 constitution, Puerto Rico is a Commonwealth and is permitted a degree of autonomy similar to that of a state of the Union. Unable to translate the word into spanish, the convention adopted a translation inspired by the Irish Free State called “Estado Libre Asociado” (ELA) to represent the compact between the people of Puerto Rico and the United States, which is literally translated into english as “Associated Free State” . The convention on February 4 of 1952 approved resolution 22 which chose in english the word “Commonwealth,” meaning a “politically organized community” or “State,” which is simultaneously connected by a compact or treaty to another political system. Prior to approving the new constitution, the Constitutional Convention specified the name by which the body politic would be known.

Puerto Ricans expressed their support for this measure in a 1951 referendum, which gave voters a yes-or-no choice for the commonwealth status, defined as a ‘permanent association with a federal union.’ A second referendum was held to approve the constitution, which was adopted in 1952. In 1950, the US Congress afforded Puerto Ricans the right to organize a constitutional convention, contingent on the results of a referendum, where the electorate would determine if they wished to organize their own government pursuant to a constitution of their own choosing. Puerto Rico divided into 78 municipalities, each of which elect a mayor and a municipal legislature. Members of the Judicial branch are appointed by the governor and approved by the senate.

The governor as well as legislators are elected by popular vote every four years. The legal system is based on a mix of the Civil Law and the Common Law systems. The government of Puerto Rico is based on the Republican system composed of 3 branches: the Executive branch headed by the Governor, the Legislative branch consisting of a bicameral Legislative Assembly (a Senate and a House of Representatives) and the Judicial branch. At its deepest point (named Milwaukee Depth), it is 27,493 feet deep (8,380 m), or about 5.2 miles.

The trench is 1,090 miles long and about 60 miles wide. Lying about 75 miles north of Puerto Rico in the Atlantic Ocean at the boundary between the Caribbean and North American plates is the Puerto Rico Trench, the largest and deepest trench in the Atlantic. It originated off the coast of Aguadilla and was accompanied by a tsunami. The most recent major earthquake occurred on October 11, 1918 and had an estimated magnitude of 7.5 on the Richter scale.

These seismic events, along with landslides, represent some of the most dangerous geologic hazards in the island and in the northeastern Caribbean. These stresses may cause earthquakes and tsunamis. This means that it is currently being deformed by the tectonic stresses caused by the interaction of these plates. Puerto Rico lies at the boundary between the Caribbean and North American plates.

These rocks may represent part of the oceanic crust and are believed to come from the Pacific Ocean realm. The oldest rocks are approximately 190 million years old (Jurassic) and are located at Sierra Bermeja in the southwest part of the island. Most of the caverns and karst topography on the island occurs in the northern Oligocene to recent carbonates. Puerto Rico is composed of Cretaceous to Eocene volcanic and plutonic rocks, which are overlain by younger Oligocene to recent carbonates and other sedimentary rocks.

The south is thus drier and hotter than the north region. Most of these rivers are born in the "Cordillera Central." The rivers in the northern region of the island are bigger and with higher flow capacity than those of the south region. Puerto Rico has nine lakes (none of them natural) and more than 50 rivers. The capital city, San Juan, is located on the main island's north coast.

Another important peak is El Yunque, located in the Caribbean National Forest, with a maximum elevation of 1,065m. The highest elevation point of Puerto Rico, Cerro de Punta (1338 meters), is located in this range. The main mountainous range is called "La Cordillera Central" (The Central Range). Some beautiful beaches on the north-west side of the island are Jobos Beach, Maria's Beach, Domes Beach and Sandy Beach.

It is mostly mountainous with large coastal areas in the north and south regions of the island. The mainland measures some 170 km by 60 km (105 miles by 35 miles). Mona is uninhabited through large parts of the year except for employees of the Puerto Rico Department of Natural Resources. Of the latter five, only Culebra and Vieques are inhabited year-round.

Puerto Rico consists of the main island of Puerto Rico and various smaller islands, including Vieques, Culebra, Mona, Desecheo, and Caja de Muertos. The Legislature, as well as the political parties, were gearing up in early 2006 to lobby Congress to address the Presidential task force recommendations. Bush called on Congress to hold the first federally-authorized vote ever for Puerto Rican voters to decide whether they wished to continue their current relationship, described as an unincorporated territory subject to the will of Congress, or whether they wish to choose in a subsequent vote among permanent non-territorial options, which the report enumerates as statehood or independence. On December 22, 2005, a task force created by President Clinton and appointed by President George W.

The only major independence party on the island, the Partido Independentista Puertorriqueňo or PIP, usually receives 5-6% of the votes in the elections though there are several smaller independence groups like the Macheteros (or Boricua Popular Army). In the latest status referendum of 1998, commonwealth status (or "None of the above") won over statehood with 50.2% of the votes, and support for the pro-statehood party (Partido Nuevo Progresista or PNP) and the pro-commonwealth party (Partido Popular Democrático or PPD) is about equal. Narrow victories by commonwealth supporters over statehood advocates have not yielded substantial changes in the relationship between the island and the United States. Three locally-authorized plebiscites have been held in recent decades to decide whether Puerto Rico should request independence, enhanced commonwealth status, or statehood.

Still, Puerto Rico continues to struggle to define its political status. Present-day Puerto Rico has become a major tourist destination and a leading pharmaceutical and manufacturing center. During the 1950s Puerto Rico experienced a rapid industrialization, with such projects as Operation Bootstrap which aimed to industrialize Puerto Rico's economy from agriculture-based into manufacturing-based. Puerto Rico adopted its own constitution in 1952 which adopted the name "commonwealth" for the body politic and which is used by many as the name of Puerto Rico's current relationship with the United States [6][7].

Subsequently, Truman allowed for a genuinely democratic referendum in Puerto Rico to determine whether Puerto Ricans desired to draft their own constitution [5]. Truman. On November 1, 1950, Puerto Rican nationalists Griselio Torresola and Oscar Collazo attempted to assassinate President Harry S. In 1945 there were 13,000 Puerto Ricans living in New York City - by 1955 there were 700,000, and by the mid-1960s there were over a million.

in search of better economic conditions. Starting at this time, there was heavy migration from Puerto Rico to the continental U.S.A. Luis Muñoz Marín would become the first elected governor of Puerto Rico in the 1948 general elections. In 1947, the United States granted the right to democratically elect the governor of Puerto Rico.

Piñero. Truman in 1946 of the first Puerto Rican-born governor, Jesus T. Change in the nature of governance of the island came about during the latter years of the Roosevelt–Truman administrations, as a form of compromise spearheaded by Luis Muñoz Marín and others, and which culminated with the appointment by President Harry S. government and opted to create the "commonwealth" option as an eventual stepping stone to full independence.

Múñoz Rivera initially favored independence, but saw a severe decline of the Puerto Rican economy, as well as growing violence and uprisings, at the hands of the U.S. Federal Government. He would eventually die by what he claimed was a conspiracy set in place by the U.S. Some political leaders demanded change; some, like Pedro Albizu Campos, would lead a nationalist (The Puerto Rican Nationalist Party) movement in favor of independence.

Natural disasters and the Great Depression impoverished the island. citizenship so that they could be recruited as soldiers for WWI. In 1917, the Jones-Shafroth Act approved by the United States Congress granted Puerto Ricans U.S. The twentieth century began under the military regime of the United States with officials, including the governor, appointed by the President of the United States.

Spain was forced to cede Puerto Rico, along with Cuba and the Phillippines, to the United States under the Treaty of Paris (1898) [4]. On July 25, 1898 at the outbreak of the Spanish–American War, Puerto Rico, being a colony of Spain, was invaded by the United States of America with a landing at Guánica. The charter maintained a governor appointed by Spain, who held the power to annul any legislative decision he disagreed with, and a partially elected parliamentary structure. The following year, Puerto Rico's first, but short-lived, autonomous government was organized.

In 1897, Múñoz Rivera and others persuaded the liberal Spanish government to agree to a Charters of Autonomy for Cuba and Puerto Rico. Later, another political stronghold was the autonomist movement originated by Román Baldorioty de Castro and, toward the end of the century, by Luis Muñoz Rivera. Leaders of this independence movement included Ramón Emeterio Betances, considered the "father" of the Puerto Rican nation, and other political figures such as Segundo Ruiz Belvis. The uprising was easily and quickly crushed.

Toward the end of the 19th century, poverty and political estrangement with Spain led to a small but significant uprising in 1868 known as "El Grito de Lares". After the rapid gains of independence by the South and Central American states in the first part of the century, Puerto Rico and Cuba became the sole New World remnants of the large Spanish empire. Nineteenth century reforms augmented the population and economy, and expanded the local character of the island. The representative Ramon Power y Giralt died soon after arriving in Spain; and constitutional reforms were reversed when autocratic monarchy was restored.

In 1809, while Napoleon occupied the majority of the Iberian peninsula, a populist assembly based in Cadiz recognized Puerto Rico as an overseas province of Spain with the right to send representatives to the Spanish Court. The French, Dutch and English made attempts to capture Puerto Rico, but failed to wrest long-term occupancy of the island. Fortresses such as La Fortaleza, El Castillo San Felipe del Morro and El Castillo de San Cristóbal were built. Concerned about threats from its European enemies, over the centuries various forts and walls were built to protect the port of San Juan.

However, colonial emphasis during the late 17th–18th centuries focused on the more prosperous mainland territories, leaving the island impoverished of settlers. Puerto Rico briefly became an important stronghold and port for the Spanish empire in the Caribbean. The island was soon colonized by the Spanish and African slaves were introduced as labour to replace the decreasing populations of Taino indians who were being forced to work for the Spanish crown. Spanish conquistador Juan Ponce de León became the island's first governor to take office, while Vicente Yáñez Pinzón was the first appointed governor, although he never arrived on the island.

Originally named San Juan Bautista, in honor of Saint John the Baptist, the island ultimately took the name of Puerto Rico (Rich Port), while the name San Juan is now delegated to its capital and largest city. However, they did not succeed. The Pinzón family was given one year by the Spanish court to start a settlement in Puerto Rico which would give them a claim to the island. Some say that Puerto Rico was not discovered by Columbus but by Martin Alonzo Pinzón in 1492 when he separated from Columbus and went exploring on his own.

The Taínos called the island "Borikén." The first European contact was made by Christopher Columbus during his second voyage to the Antilles, on November 19, 1493. When Europeans first arrived, the island of Puerto Rico was inhabited by a group of Arawak Indians known as Taínos. They maintained this dominance until the arrival of the Spanish in 1493. Between the 7th and 11th century the Taíno culture develops in the islanda and by approximately the 1000 the Taíno culture had become the dominant culture in the island.

Afterwards, between 120 and 400 AD, the Igneri, a tribe that preceded both the Caribs and Taínos, arrived on the island [3]. An archeological dig in the island of Vieques in 1990 found the remains of what is believed to be an Arcaico man (named Puerto Ferro man) which was dated to 1900 BC [2]. The first indigenous settlers of Puerto Rico were the Arcaico. The first comprehensive book on the history of Puerto Rico was written by Fray Iñigo Abbad y Lassiera in 1776, 283 years after the first Spaniards arrived on the island [1].

What is known today comes from archeological findings and from the writings of oral accounts of the Spanish. The history of the island of Puerto Rico before Christopher Columbus arrived is very limited. . "in the nature of a compact", but opponents of Commonwealth disagree: according to them, Puerto Rico is no more than an unincorporated organized territory of the U.S., subject to the plenary powers of the United States Congress.

Supporters of maintaining the status quo (i.e., Commonwealth status) insist that upon attaining this status, Puerto Rico entered into a voluntary association with the U.S. The nature of Puerto Rico's political relationship with the United States is the subject of ongoing debate in the island. Puerto Rico, the smallest of the Greater Antilles, includes the main island of Puerto Rico and a number of smaller islands and keys, including Mona, Vieques, and Culebra. The Commonwealth of Puerto Rico (Spanish: Estado Libre Asociado de Puerto Rico) is a commonwealth of the United States located east of the Dominican Republic in the northeastern Caribbean.

...that the largest single-aperture telescope ever to be constructed is the Arecibo Observatory located in the city by the same name in Puerto Rico?. ...that the first opera in history to be recorded was Pagliacci by Ruggiero Leoncavallo and that the recording was made by tenor Antonio Paoli?. Teofilo Marxuach when an armed German supply ship tried to force it's way out of the bay?. ...that the first shot fired by the United States in World War I was in Puerto Rico and not in Europe? It was fired by Lt.

...that Puerto Rico once had a President? His name was Francisco Ramirez Medina.. Tree - Ceiba or Kapok (ceiba pentandra). Flower - Flor de Maga or Puerto Rican hibiscus (Thespesia grandiflora or Maga grandiflora). Bird - Reinita mora (Spindalis portoricensis).

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