|UTC time||1942-08-06 23:37:02|
|Local date||August 6, 1942|
|Magnitude|| Mw 7.7 |
|Depth||35 km (22 mi)|
The 1942 Guatemala earthquake occurred at 17:37 local time on August 6 and had ratings of 7.7 on the moment magnitude scale and 7.9 on the surface wave magnitude scale. The epicenter was located off the southern coast of Guatemala,and it was one of the strongest earthquakes ever recorded there.
The earthquake caused widespread damage in the west-central highlands of Guatemala. Thirty-eight people died in the earthquake. Landslides caused by the combination of the earthquake and the heavy seasonal rains destroyed roads, the Inter-American Highway, and telegraph lines. In Tecpán Guatemala, more than 60% of the houses were demolished. Damage was reported in some buildings in Antigua Guatemala, including the Palacio de Los Capitanes Generales and some catholic churches.The earthquake could also be felt strongly in Mexico and El Salvador.
This earthquake was a lower crustal intraplate earthquake with a compressional focal mechanism. [ page needed ] Tensional activity has been dominant along the down-dip edge along the 1942 rupture zone. It was estimated that earthquakes near the Middle America Trench with magnitudes of about 7.5~8.0 occurred at intervals of 94 ± 54 yrs in southwestern Guatemala. Such historical earthquakes included the earthquakes in 1765, 1902, and 1942.
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.
Hiroo Kanamori is a Japanese seismologist who has made fundamental contributions to understanding the physics of earthquakes and the tectonic processes that cause them.
An interplate earthquake is an earthquake that occurs at the boundary between two tectonic plates. Earthquakes of this type account for more than 90 percent of the total seismic energy released around the world. If one plate is trying to move past the other, they will be locked until sufficient stress builds up to cause the plates to slip relative to each other. The slipping process creates an earthquake with relative displacement on either side of the fault, resulting in seismic waves which travel through the Earth and along the Earth's surface. Relative plate motion can be lateral as along a transform fault boundary, vertical if along a convergent boundary or a divergent boundary, and oblique, with horizontal and lateral components at the boundary. Interplate earthquakes associated at a subduction boundary are called megathrust earthquakes, which are the most powerful earthquakes.
The 1946 Aleutian Islands earthquake occurred near the Aleutian Islands, Alaska on April 1. The shock had a moment magnitude of 8.6 and a maximum Mercalli intensity of VI (Strong). It resulted in 165–173 casualties and over $26 million in damage. The seafloor along the fault was elevated, triggering a Pacific-wide tsunami with multiple destructive waves at heights ranging from 45–130 ft. The tsunami obliterated the Scotch Cap Lighthouse on Unimak Island, Alaska among others, and killed all five lighthouse keepers. Despite the destruction to the Aleutian Island Unimak, the tsunami had almost an imperceptible effect on the Alaskan mainland.
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 1902 Guatemala earthquake occurred on April 18 at 8:23 pm with a moment magnitude of 7.5 and a maximum Mercalli intensity of VIII (Severe). The rupture initiated at a depth of 25 km (16 mi) and the duration was 1 to 2 minutes.
The 1946 Nankai earthquake was a great earthquake in Nankaidō, Japan. It occurred on December 21, 1946, at 04:19 JST. The earthquake measured between 8.1 and 8.4 on the moment magnitude scale, and was felt from Northern Honshū to Kyūshū. It occurred almost two years after the 1944 Tōnankai earthquake, which ruptured the adjacent part of the Nankai megathrust.
The 1896 Sanriku earthquake was one of the most destructive seismic events in Japanese history. The 8.5 magnitude earthquake occurred at 19:32 on June 15, 1896, approximately 166 kilometres (103 mi) off the coast of Iwate Prefecture, Honshu. It resulted in two tsunamis which destroyed about 9,000 homes and caused at least 22,000 deaths. The waves reached a then-record height of 38.2 metres (125 ft); this would remain the highest on record until waves from the 2011 Tōhoku earthquake exceeded that height by more than 2 metres.
The 1906 Ecuador–Colombia earthquake occurred at 15:36 UTC on January 31, off the coast of Ecuador, near Esmeraldas. The earthquake had a moment magnitude of 8.8 and triggered a destructive tsunami that caused at least 500 casualties on the coast of Colombia.
The 1965 Rat Islands earthquake occurred at 05:01 UTC, on 4 February. It had a magnitude of 8.7 and triggered a tsunami of over 10 m on Shemya Island, but caused very little damage.
The 1978 Miyagi earthquake occurred at 17:14 local time on 12 June. It had a surface wave magnitude of 7.7, JMA magnitude 7.4, and triggered a small tsunami. The earthquake reached a maximum intensity of Shindo 5 in Sendai and caused 28 deaths and 1,325 injuries.
The 1982 El Salvador earthquake occurred southeast of San Salvador on 19 June at 00:21 local time. This undersea earthquake struck offshore in the Pacific Ocean and had a surface wave magnitude of 7.2 and a maximum Mercalli intensity of VII. Occurring adjacent to a subduction zone at the Middle America Trench, this normal-slip shock left at least 16 and as many as 43 people dead, and many injured, and also inflicted $5 million in damage.
The 1994 offshore Sanriku earthquake occurred on December 28, 1994, at 12:19 UTC. This was a magnitude Mw 7.7 earthquake with epicenter located in the Pacific Ocean at about 180 km east of Hachinohe, Aomori. Three people were reported dead and more than 200 injured; 48 houses were completely destroyed. Road damage and power outages were reported. Liquefaction occurred in the Hachinohe Port area. The intensity reached shindo 6 in Hachinohe, Aomori, about 187.6 km from epicenter. It could be felt in Tokyo, about 632.9 km from epicenter, with shindo 2. The Japanese Meteorological Agency put the magnitude at MJMA 7.5. Slip associated with this earthquake continued for more than a year and it has been termed an 'ultra-slow earthquake'.
A tsunami earthquake triggers a tsunami of a magnitude that is very much larger than the magnitude of the earthquake as measured by shorter-period seismic waves. The term was introduced by Hiroo Kanamori in 1972. Such events are a result of relatively slow rupture velocities. They are particularly dangerous as a large tsunami may arrive at a coastline with little or no warning. A tsunami is a sea wave of local or distant origin that results from large-scale seafloor displacements associated with large earthquakes, major submarine slides, or exploding volcanic islands.
The 1928 Talca earthquake occurred on 1 December at 00:06 local time near Curepto, Maule Region, Chile, with an estimated magnitude of 7.6 MW, 8.3 MS and 7.9 ML. In Talca, it lasted 1 minute 45 seconds.
The 1937 Orizaba earthquake occurred on July 26 at 03:47 UTC, near Orizaba, Veracruz, Mexico. It had a magnitude of 7.3 on the surface wave magnitude scale. Thirty four people were reported dead. Damage was reported in Esperanza, Puebla. This was an intraplate earthquake within the subducting Cocos Plate.
The 1971 Solomon Islands earthquakes occurred in the northern part of the Solomon Islands, within Papua New Guinea as a doublet earthquake. The first large shock occurred on July 14 at 06:11 UTC with a magnitude of Mw 8.0. The second large event occurred on July 26 at 01:23 UTC with a magnitude of Mw 8.1. The initial event on July 14 caused a tsunami, which was observed in Rabaul. The earthquake of July 26 triggered a tsunami with a 3.4 m (11 ft) runup in New Britain.
The 1981 Playa Azul earthquake occurred on October 24, 1981, at 21:22 local time. It was located near Playa Azul, Michoacán, Mexico. The magnitude of the earthquake was Mw 7.2, or Ms 7.3. Three deaths were reported, two from Michoacán and one from Mexico City. Some buildings were damaged in both Michoacán and Mexico City. A small tsunami was registered in Acapulco with a maximum height of 9 cm.
The 1982 Ometepec earthquake that struck Mexico's southwestern coast near Ometepec (Guerrero) on 7 June was a doublet earthquake that ruptured in two steps. The first happened at 06:52 UTC, the second five hours later at 10:59 UTC. Estimated magnitudes are 6.9 and 7.0 on the Ms scale, and 5.8 and 6.0 on the mb scale. The maximum MM intensities were VII and VIII, respectively.