  | |
| UTC time | 1970-07-31 17:08:05 |
|---|---|
| ISC event | 794176 |
| USGS-ANSS | ComCat |
| Local date | July 31, 1970 |
| Local time | 12:08:05 |
| Magnitude | 8.0 Mw [1] |
| Depth | 645 km (401 mi) [1] |
| Epicenter | 1°36′S72°32′W / 1.6°S 72.53°W Coordinates: 1°36′S72°32′W / 1.6°S 72.53°W [1] |
| Areas affected | Colombia |
| Max. intensity | IV (Light) |
| Casualties | 1 dead, several injured [2] |
The 1970 Colombia earthquake occurred in Colombia on July 31.
The shock killed one person and injured several others. Because it was a deep-focus earthquake, shaking occurred over an extensive area, including San Juan, Bogotá, Caracas, Buenos Aires, and São Paulo; it was felt as far north as Mexico City. [3] Its depth forestalled more serious casualties, [3] and there were no aftershocks. [4]
The depth of the earthquake prompted scientists in South America to install seismometer networks focused on long-period earthquakes. [3] Until the 1994 Bolivia earthquake, the 1970 Colombia earthquake was famous among seismologists as the largest deep earthquake. [5]
A study completed by Dziewonski and Gilbert (1974) determined that the earthquake had featured isotropic compression, or an increase in density near the rupture point similar to an implosion; [6] this was released to great controversy. [5] They also claimed that the compression had been initiated 80 seconds before the actual earthquake's short-period shaking. Many studies have reached differing conclusions including a dearth of isotropic movement, and many scientists feel that resolution created errors in Dziewonski and Gilbert's findings. [7] In 1997, Russakoff, Ekstrom, and Tromp reassessed their findings utilizing more advanced equipment that factored in shear wave splitting and coupling (the measure of how tightly locked two sides of a fault or plate are) and confirmed that there was very little isotropic compression. [5]
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial, oceanic, atmospheric, and artificial processes such as explosions. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of Earth motion as a function of time is called a seismogram. A seismologist is a scientist who does research in seismology.
The moment magnitude scale is a measure of an earthquake's magnitude based on its seismic moment. It was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori. Similar to the local magnitude scale (ML ) defined by Charles Francis Richter in 1935, it uses a logarithmic scale; small earthquakes have approximately the same magnitudes on both scales.
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Adam Marian Dziewoński was a Polish-American geophysicist who made seminal contributions to the determination of the large-scale structure of the Earth's interior and the nature of earthquakes using seismological methods. He spent most of his career at Harvard University, where he was the Frank B. Baird, Jr. Professor of Science.
The 1992 Big Bear earthquake occurred at 08:05:33 PDT on June 28 in Big Bear Lake, California, with a moment magnitude of 6.5 and a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale. The earthquake occurred at a relatively shallow depth of 5 kilometers (3.1 mi).
The 1933 Baffin Bay earthquake struck Greenland and the Northwest Territories, Canada with a moment magnitude of 7.7 at 18:21:35 Eastern Time Zone on November 20.
The 1915 Pleasant Valley earthquake occurred at 22:53:21 on October 2 in north-central Nevada. With a moment magnitude of 6.8 and a maximum Mercalli intensity of X (Extreme), it was the strongest earthquake ever recorded in the state.
This list of 20th-century earthquakes is a global list of notable earthquakes that occurred in the 20th century. After 1900 most earthquakes have some degree of instrumental records and this means that the locations and magnitudes are more reliable than for earlier events. To prevent this list becoming unmanageable, only those of magnitude 6 and above are included unless they are notable for some other reason.
The 1991 Uttarkashi earthquake occurred at 02:53:16 Indian Standard Time (UTC+05:30) on 20 October with a moment magnitude of 6.8 and a maximum Mercalli intensity of IX (Violent). This thrust event was instrumentally recorded and occurred along the Main Central Thrust in the Uttarkashi and Gharwal regions of the Indian state of Uttarakhand. High intensity shaking resulted in the deaths of at least 768 people and the destruction of thousands of homes.
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The 1996 Biak earthquake, or the 1996 Irian Jaya earthquake, occurred on February 17 at 14:59:30 local time near Biak Island, Indonesia. The earthquake had a moment magnitude of 8.2 and a maximum Mercalli intensity of IX (Violent). The run-up height of the generated tsunami reached 7 meters (23 ft). One-hundred and sixty-six people were reported dead, 423 were injured, and 5,090 were made homeless.
The 1997 Cariaco earthquake occurred on July 9 at 15:24:14 local time with a moment magnitude of 6.9 and a maximum Mercalli intensity of VIII (Severe). With its epicenter near Cariaco, Venezuela, at least 81 people were killed and over 500 were injured. Disruption of power, telephone, and water services was reported. This earthquake was felt in much of northeastern Venezuela and could also be felt in Trinidad and Tobago. This earthquake was on the strike-slip El Pilar Fault.
The Sagaing Fault is a major fault in Burma, a mainly continental right-lateral transform fault between the Indian Plate and Sunda Plate. It links the divergent boundary in the Andaman Sea with the zone of active continental collision along the Himalayan front. It passes through populated cities of Mandalay, Yamethin, Pyinmana, the capital Naypyidaw, Toungoo and Pegu before dropping off into the Gulf of Martaban, running for a total length of over 1200 kilometers.
James Freeman Gilbert was an American geophysicist, best known for his work with George E. Backus on inverting geophysical data, and also for his role in establishing an international network of long-period seismometers.
A deep-focus earthquake in seismology is an earthquake with a hypocenter depth exceeding 300 km. They occur almost exclusively at convergent boundaries in association with subducted oceanic lithosphere. They occur along a dipping tabular zone beneath the subduction zone known as the Wadati–Benioff zone.
The 1954 Chlef earthquake struck Chlef Province in Algeria on September 9 at 02:04:43 local time. The shock measured 6.7 on the moment magnitude scale and had a maximum Mercalli intensity of XI (Extreme). It destroyed Chlef, then named Orléansville, leaving over 1,243 people dead and 5,000 injured. Damage was estimated at $6 million. It was followed by multiple aftershocks. Algeria faces annual earthquakes and has undergone several changes to its earthquake building codes since its first earthquake engineering regulations from 1717.
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The 1976 Longling earthquake in Yunnan Province, People's Republic of China, was a doublet earthquake, with two main shocks striking just east of Longling at 12:23:20 and 14:00:22 UTC. The magnitudes were estimated at 6.7 and 6.6, respectively, on the Mw(GCMT) scale, and 6.9 and 7.0 on the Ms scale; Chinese sources put these at 7.4 and 7.3 on the Ms7 scale. The region is noted for the quantity and intensity of its earthquakes, and the complexity of its tectonics, which are closely related to the collision between the Indian and Eurasian tectonic plates.
The 1979 Ghaenat earthquakes were a series of large earthquakes in Qaen County, Khorasan Province, northeast Iran, near the Afghanistan border. The first mainshock, known as the Korizan earthquake with a surface wave magnitude (Ms ) of 6.6 and moment magnitude (Mw ) of 6.8, struck on November 14, while the Ms 7.1 or Mw 7.2 Koli-Boniabad earthquake struck on Nobemver 27. The two mainshocks were assigned a maximum Modified Mercalli intensity of VIII (Severe) and IX (Violent) respectively. The earthquakes caused extensive damage throughout northeastern Iran, killed a total of 297 to 440 people and left at least 79 injured.
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