Frequency of Earthquakes Worldwide The following table lists the frequency of earthquakes worldwide, according to magnitude and annual average. DescriptorMagnitudeAnnual average Great8 or higher11 Major7–7.9172 Strong6–6.91342 Moderate5–5.91,3192 Light4–4.9c. 13,000 Minor3–3.9c. 130,000 Very minor2–2.9c. 1,300,000 1. Based on observations since 1900. 2. Based on observations since 1990. NOTE: The NEIC estimates that several million earthquakes occur in the world each year. Many go undetected because they hit remote areas or have very small magnitudes. Source:National Earthquake Information Center, U.S. Geological Survey.

The Severity of an Earthquake Source:National Earthquake Information Center, U.S. Geological Survey Earthquakes are the result of forces deep within Earth's interior that continuously affect its surface. The energy from these forces is stored in a variety of ways within the rocks. When this energy is released suddenly—by shearing movements along faults in the crust of Earth, for example—an earthquake results. The area of the fault where the sudden rupture takes place is called the focus or hypocenter of the earthquake. The point on Earth's surface directly above the focus is called the epicenter of the earthquake. The severity of an earthquake can be expressed in terms of both intensity and magnitude. The two terms are quite different, however, and they are often confused. Intensity is based on the observed effects of ground shaking on people, buildings, and natural features. It varies from place to place within the disturbed region depending on the location of the observer with respect to the earthquake epicenter. Magnitude is related to the amount of seismic energy released at the hypocenter of the earthquake. It is based on the amplitude of the earthquake waves recorded on instruments, which have a common calibration. Magnitude is thus represented by a single, instrumentally determined value. The Richter Magnitude Scale Seismic waves are the vibrations from earthquakes that travel through Earth; they are recorded on instruments called seismographs. Seismographs record a zigzag trace that shows the varying amplitude of ground oscillations beneath the instrument. Sensitive seismographs, which greatly magnify these ground motions, can detect strong earthquakes from sources anywhere in the world. The time, location, and magnitude of an earthquake can be determined from the data recorded by seismograph stations. The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included in the magnitude formula to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude of 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value. Although the Richter Scale has no upper limit, the largest known shocks have had magnitudes in the 8.8 to 8.9 range. Why Are There So Many Earthquake Magnitude Scales? Earthquake size, as measured by the Richter Scale, is a well-known, but not well understood, concept. What is even less well understood is the proliferation of magnitude scales and their relation to Richter's original magnitude scale. Richter's magnitude scale was first created for measuring the size of earthquakes occurring in southern California, using relatively high-frequency data from nearby seismograph stations. This magnitude scale was referred to as ML, with the L standing for local. As more seismograph stations were installed around the world, it became apparent that the method developed by Richter was strictly valid only for certain frequency and distance ranges. In order to take advantage of the growing number of globally distributed seismograph stations, new magnitude scales that are an extension of Richter's original idea were developed. These include body-wave magnitude, “mb,” and surface-wave magnitude, “MS.” Each is valid for a particular frequency range and type of seismic signal. In its range of validity each is equivalent to the Richter magnitude. Because of the limitations of all three magnitude scales—ML, mb, and MS—a new, more uniformly applicable extension of the magnitude scale, known as moment magnitude, or “MW,” was developed. In particular, for very large earthquakes moment magnitude gives the most reliable estimate of earthquake size. New techniques that take advantage of modern telecommunications have recently been implemented, allowing reporting agencies to obtain rapid estimates of moment magnitude for significant earthquakes. So nowadays, when most seismologists announce a magnitude number, they are rarely referring to the Richter Scale. The Modified Mercalli Intensity Scale The effect of an earthquake on Earth's surface is called the intensity.

Tsunami in Japan 2011: Waves Stirred Up by Earthquake Cause Wide Destruction Learn about the science behind tsunamis and earthquakes Source: U.S. Geological Survey Tsunami. Relief Effort in Japan Tsunami in Japan Japanwas hit by a 9.0 magnitude earthquakeon March 11, 2011, that triggered a deadly 23-foot tsunami in the country's north. The giant waves deluged cities and rural areas alike, sweeping away cars, homes, buildings, a train, and boats, leaving a path of death and devastation in its wake. Video footage showed cars racing away from surging waves. The earthquake—the largest in Japan's history—struck about 230 miles northeast of Tokyo. The Pacific Tsunami Warning Center issued warnings for Russia, Taiwan, Hawaii, Indonesia, the Marshall Islands, Papua New Guinea, Australia, and the west coasts the U.S., Mexico, Central America, and South America. According to the official toll, the disasters left 15,839 dead, 5,950 injured, and 3,642 missing. Earthquake Causes Nuclear Disaster What's more, cooling systems in one of the reactors at the Fukushima Daiichi Nuclear Power Station in the Fukushima prefecture on the east coast of Japan failed shortly after the earthquake, causing a nuclear crisis. This initial reactor failure was followed by an explosion and eventual partial meltdowns in two reactors, then by a fire in another reactor which released radioactivity directly into the atmosphere. The nuclear troubles were not limited to the Daiichi plant; three other nuclear facilities also reported problems. More than 200,000 residents were evacuated from affected areas. On April 12, Japan raised its assessment of the situation at the Fukushima Daiichi nuclear power plant to Level 7, the worst rating on the international scale, putting the disaster on par with the 1986 Chernobyl explosion. Developed by the International Atomic Energy Agency (IAEA) along with countries who use nuclear energy, the scale defines level 7 as a nuclear accident that involves "widespread health and environmental effects" and the "external release of a significant fraction of the reactor core inventory." Almost two months later, the IAEA called the status of the Fukushima Daiichi nuclear plant "very serious." At a news conference on March 13, Prime Minister Naoto Kan, who later gave the disaster the name "Great East Japan Earthquake", emphasized the gravity of the situation: "I think that the earthquake, tsunami, and the situation at our nuclear reactors makes up the worst crisis in the 65 years since the war. If the nation works together, we will overcome." The government called in 100,000 troops to aid in the relief effort. The deployment was the largest since World War II. The tsunami in Japan recalled the 2004 disaster in the Indian Ocean. On Dec. 26, a 9.0 magnitude earthquake—the largest earthquakein 40 years—ruptured in the Indian Ocean, off the northwest coast of the Indonesian island of Sumatra. The earthquake stirred up the deadliest tsunamiin world history, so powerful that the waves caused loss of life on the coast of Africa and were even detected on the East Coast of the United States. More than 225,000 people died from the disaster, a half a million were injured, and millions were left homeless. Seestatistics on Deadliest Tsunamisand Deadliest Earthquakes. The Science of Tsunami A tsunami(pronounced soo-NAHM-ee) is a series of huge waves that occur as the result of a violent underwater disturbance, such as an earthquakeor volcanic eruption. The waves travel in all directions from the epicenter of the disturbance. The waves may travel in the open sea as fast as 450 miles per hour. As they travel in the open ocean, tsunami waves are generally not particularly large—hence the difficulty in detecting the approach of a tsunami. But as these powerful waves approach shallow waters along the coast, their velocity is slowed and they consequently grow to a great height before smashing into the shore. They can grow as high as 100 feet; the Indian Ocean tsunami generated waves reaching 30 feet. Tsunamiis the Japanese word for "harbor wave." They are sometimes mistakenly referred to as tidal waves, but tsunamis have nothing to do with the tides. Tsunamis have been relatively rare in the Indian Ocean, and are most common in the Pacific Ocean.

Spain: Kings, Queens, Prime Ministers Kings and queens Carlos II(1665–1700) Felipe V(1700–1724, 1724–1746) Luis I (1724) Fernando VI(1746–1759) Carlos III(1759–1788) Carlos IV(1788–1808) Joaquín Murat, gran duque de Berg (1808) Fernando VII(1808–1833) Isabel II(1833–1868) María Cristina, regent (1833–1840) Baldomero Espartero, duque de la Victoria, regent (1840–1843) Carlos VI (1860) Amadeo I(1871–1873) Carlos VII (1872–1876) Alfonso XII(1874–1885) María Cristina, regent (1885–1886, 1886–1902) Alfonso XIII(1886–1931) Juan Carlos I(1975– ) Prime Ministers Francisco Franco(1938–1973), also head of state (1936–1975) Luis Carrero Blanco(1973) Torcuato Fernández Miranda, acting (1973–1974) Carlos Arias Navarro (1974–1976) Adolfo Suárez González (1976–1981) Leopoldo Calvo Sotelo y Bustelo (1981–1982) Felipe González Márquez(1981–1996) José María Aznar(1996–2004) José Luis Rodríguez Zapatero (2004– )

Sweden: Kings and Queens Kings and Queens Karl XII(1697–1718) Ulrica Eleonora (1719–1720) Fredrik I (1720–1751) Adolf Fredrik (1751–1771) Gustaf III(1771–1792) Gustaf IV Adolf(1792–1809) Karl XIII(1809–1818) Karl XIV Johan(1818–1844) Oscar I(1844–1859) Karl XV(1859–1872) Oscar II(1872–1907) Gustaf V(1907–1950) Gustaf VI Adolf(1950–1973) Carl XVI Gustaf(1973– )