In seismology, a buried rupture earthquake, or blind earthquake, is an earthquake which does not produce a visible offset in the ground along the fault (as opposed to a surface rupture earthquake, which does). When the fault in question is a thrust fault, the earthquake is known as a blind thrust earthquake.
Recorded ground motions of large surface-rupture earthquakes are weaker than the ground motions from buried rupture earthquakes. [1]
The asperity for a buried rupture earthquakes is in area deeper than roughly 5 kilometres (3.1 mi). Examples are the Loma Prieta earthquake, Northridge earthquake, and the Noto Hanto earthquake. [2]
As compared to the seabed surface rupture case, uplifted water outside the fault plane in buried rupture earthquakes makes for large tsunami waves. [3]
An earthquake is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from those that are so weak that they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. The word tremor is also used for non-earthquake seismic rumbling.
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or other planetary bodies. It 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.
A blind thrust earthquake occurs along a thrust fault that does not show signs on the Earth's surface, hence the designation "blind". Such faults, being invisible at the surface, have not been mapped by standard surface geological mapping. Sometimes they are discovered as a by-product of oil exploration seismology; in other cases their existence is not suspected.
Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthquakes are the planet's most powerful, with moment magnitudes (Mw) that can exceed 9.0. Since 1900, all earthquakes of magnitude 9.0 or greater have been megathrust earthquakes.
Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. Magnitude scales vary on what aspect of the seismic waves are measured and how they are measured. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used.
The 1944 Tōnankai earthquake occurred at 13:35 local time on 7 December. It had an estimated magnitude of 8.1 on the moment magnitude scale and a maximum felt intensity of greater than 5 Shindo. It triggered a large tsunami that caused serious damage along the coast of Wakayama Prefecture and the Tōkai region. Together, the earthquake and tsunami caused 3,358 casualties.
In seismology, an earthquake rupture is the extent of slip that occurs during an earthquake in the Earth's crust. Earthquakes occur for many reasons that include: landslides, movement of magma in a volcano, the formation of a new fault, or, most commonly of all, a slip on an existing fault.
In seismology, surface rupture is the visible offset of the ground surface when an earthquake rupture along a fault affects the Earth's surface. Surface rupture is opposed by buried rupture, where there is no displacement at ground level. This is a major risk to any structure that is built across a fault zone that may be active, in addition to any risk from ground shaking. Surface rupture entails vertical or horizontal movement, on either side of a ruptured fault. Surface rupture can affect large areas of land.
The 1930 Bago (Pegu) earthquake, also known as the Swa earthquake struck Myanmar on 5 May. The moment magnitude (Mw ) 7.4 earthquake had a focal depth of 35 km (22 mi) and maximum Rossi–Forel intensity of IX. The earthquake was the result of rupture along a 131 km (81 mi) segment of the Sagaing Fault—a major strike-slip fault that runs through the country. Extensive damage was reported in the southern part of the country, particularly in Bago and Yangon, where buildings collapsed and fires erupted. At least 550, and possibly up to 7,000 people were killed. A moderate tsunami was generated along the Burmese coast which caused minor damage to ships and a port. It was felt for over 570,000 km2 (220,000 sq mi) and as far as Shan State and Thailand. The mainshock was followed by many aftershocks; several were damaging; additional earthquakes occurred in July and December, killing dozens. The December earthquake was similarly-sized which also occurred along the Sagaing Fault.
The 1812 Ventura earthquake occurred on the morning of December 21 at 11:00 Pacific Standard Time (PST). The 7.1–7.5 magnitude earthquake, with a Modified Mercalli intensity scale rating of X (Extreme), along with its resulting tsunami, caused considerable damage to present-day Santa Barbara and Ventura County, California, which was at the time a territory of the Spanish Empire. One person was killed as a result of the earthquake while another from the aftershock. The earthquake occurred just as the region was recovering from another event on the 8th of December the same year. Both events are thought to have been related.
The 2013 Craig, Alaska earthquake struck on January 5, at 12:58 am (UTC–7) near the city of Craig and Hydaburg, on Prince of Wales Island. The Mw 7.5 earthquake came nearly three months after an Mw 7.8 quake struck Haida Gwaii on October 28, in 2012. The quake prompted a regional tsunami warning to British Columbia and Alaska, but it was later cancelled. Due to the remote location of the quake, there were no reports of casualties or damage.
The 1946 Ancash earthquake in the Andes Mountains of central Peru occurred on November 10 at 17:43 UTC. The earthquake had a surface-wave magnitude of 7.0, and achieved a maximum Mercalli intensity scale rating of XI (Extreme). About 1,400 Peruvians are thought to have died from the event.
The 1761 Lisbon earthquake and its subsequent tsunami occurred in the north Atlantic Ocean and south of the Iberian Peninsula. This violent shock which struck just after noon on 31 March 1761, was felt across many parts of Western Europe. Its direct effects were even observed far north in Scotland and Amsterdam, and to the south in the Canary Islands of Spain. The estimated surface-wave magnitude 8.5 event was the largest in the region, and the most significant earthquake in Europe since the Great Lisbon earthquake of 1755.
The 1906 Manasi earthquake (玛纳斯地震), also known as the Manas earthquake occurred in the morning of December 23, 1906, at 02:21 UTC+8:00 local time or December 22, 18:21 UTC. It measured 8.0–8.3 on the moment magnitude scale and 8.3 on the surface-wave magnitude scale. The epicenter of this earthquake is located in Manas County, Xinjiang, China. An estimated 280–300 people died and another 1,000 more were injured by the earthquake.
The 1900 Venezuelan earthquake, occurred on October 28 at between 4:30 and 4:45 am local time. This earthquake had an epicenter off Miranda State or near the Venezuelan capital Caracas, in the Cariaco Basin. It had an estimated moment magnitude of 7.6–7.7 and a surface-wave magnitude of 7.7–8.4. It had a maximum Mercalli intensity assigned VIII–X, causing landslides and liquefaction events. Many buildings were severely damaged or collapsed during the earthquake. It is thought to be the last great earthquake of the 19th century and the largest instrumentally recorded in the republic, having been felt throughout.
The 1852 Banda Sea earthquake struck on 26 November at 07:40 local time, affecting coastal communities on the Banda Islands. It caused violent shaking lasting five minutes, and was assigned XI on the Modified Mercalli intensity scale in the Maluku Islands. A tsunami measuring up to 8 m (26 ft) slammed into the islands of Banda Neira, Saparua, Haruku and Ceram. The tsunami caused major damage, washing away many villages, ships and residents. At least 60 people were killed in the earthquake and tsunami. The earthquake had an estimated moment magnitude of 7.5 or 8.4–8.8, according to various academic studies.
The 1995 Kerinci earthquake struck near Sungai Penuh in Jambi Province on the island of Sumatra, Indonesia. It earthquake occurred at 01:18 WIB local time on October 7. The earthquake measured 6.7 Mw on the moment magnitude scale, and 6.9–7.0 Ms on the surface wave magnitude scale. Between 84 and possibly even 100 people were killed in the earthquake. An extimated 4,000 buildings collapsed or were seriously damaged while a further 5,000 suffered some damage.
The 1929 Cumaná earthquake occurred on January 17 at 07:45:44 local time, affecting Venezuela. Measuring 6.7 on the moment magnitude scale (Mw ) at a depth of 10 km (6.2 mi), the earthquake severely damaged the city of Cumaná in Sucre state. The earthquake had an epicenter located offshore in the Caribbean Sea, and had a maximum Modified Mercalli intensity scale rating of IX (Violent). It lasted 30 seconds, causing major damage and a tsunami. More than 200 people were killed although the finalized death toll is unknown; possibly 1,600.
The 1657 Concepción earthquake occurred on March 15 at 20:00 local time off the coast of Concepción, Biobío Region in the Spanish Empire. The earthquake caused severe damage along the coast, and generated a large tsunami in the Bay of Concepción. At least 40 people were killed, the majority due to drowning from the tsunami. The town of Concepción was the hardest hit, with the earthquake and tsunami totally destroying it.
The 1858 Prome earthquake occurred on August 24 at 15:38 local time in British Burma. The earthquake occurred with a magnitude of 7.6–8.3 on the moment magnitude scale. It had an epicenter in near the city of Pyay (Prome), Bago. The shock was felt with a maximum Modified Mercalli intensity of XI (Extreme) for about one minute. Severe damage was reported in Bago, and off the coast of Rakhine, an island sunk.
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