  | |
| UTC time | 1942-08-24 22:50:31 |
|---|---|
| ISC event | 900444 |
| USGS-ANSS | ComCat |
| Local date | August 24, 1942 |
| Local time | 17:50 |
| Magnitude | Mw 8.2 |
| Depth | 35 km (22 mi) [1] |
| Epicenter | 14°59′S74°55′W / 14.98°S 74.92°W [1] |
| Type | Megathrust |
| Areas affected | Peru |
| Max. intensity | IX (Violent) |
| Casualties | 30 |
The 1942 Peru earthquake occurred on August 24 at 17:50 local time and was located near the border of the departments of Ica and Arequipa, Peru. It had a magnitude of Mw 8.2 or Ms 8.4. [2] [3] [4]
This is a megathrust earthquake which ruptured part of the boundary between the Nazca Plate and the South American Plate. [5] [6] In this area, the Nazca Plate is subducting beneath the South America Plate with a convergence vector of about 7.6 cm/yr. Much of the rupture zone of the 1942 earthquake overlapped with that of the 1996 Nazca earthquake. The rupture zone of the 1942 earthquake was about 40 km longer than that of the 1996 earthquake. [7] The epicenter of the 1942 earthquake was very close to, but slightly southeast of, that of the 1996 earthquake. [8] The energy released by the 1942 earthquake was about 2.5×1017 Nm. [4]
The earthquake caused 30 deaths and 25 injuries. Building damage was noteworthy in the epicentral area. About 30% of the buildings in the city of Nazca were ruined. There were slides in the hills. The intensity reached IX (Violent). [2]
This earthquake triggered a tsunami. In Callao, the amplitude of the oscillations of the tsunami was 1.6 m. [9] In Lomas, the sea receded more than 200 m, and then it flooded the settlement with injuries reported. [10]
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.
The 1957 Andreanof Islands earthquake occurred at 04:22 local time on March 9 with a moment magnitude estimated between 8.6 and 9.1 and a maximum Modified Mercalli intensity of VIII (Severe). It occurred south of the Andreanof Islands group, which is part of the Aleutian Islands arc. The event occurred along the Aleutian Trench, the convergent plate boundary that separates the Pacific Plate and the North American plates near Alaska. A basin-wide tsunami followed, with effects felt in Alaska and Hawaii, and strong waves recorded across the Pacific rim. Total losses were around $5 million.
A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake. First detected using long term strain measurements, most slow earthquakes now appear to be accompanied by fluid flow and related tremor, which can be detected and approximately located using seismometer data filtered appropriately. That is, they are quiet compared to a regular earthquake, but not "silent" as described in the past.
The Nazca Ridge is a submarine ridge, located on the Nazca Plate off the west coast of South America. This plate and ridge are currently subducting under the South American Plate at a convergent boundary known as the Peru-Chile Trench at approximately 7.7 cm (3.0 in) per year. The Nazca Ridge began subducting obliquely to the collision margin at 11°S, approximately 11.2 Ma, and the current subduction location is 15°S. The ridge is composed of abnormally thick basaltic ocean crust, averaging 18 ±3 km thick. This crust is buoyant, resulting in flat slab subduction under Peru. This flat slab subduction has been associated with the uplift of Pisco Basin and the cessation of Andes volcanism and the uplift of the Fitzcarrald Arch on the South American continent approximately 4 Ma.
The Sunda megathrust is a fault that extends approximately 5,500 km (3300 mi) from Myanmar (Burma) in the north, running along the southwestern side of Sumatra, to the south of Java and Bali before terminating near Australia. It is a megathrust, located at a convergent plate boundary where it forms the interface between the overriding Eurasian plate and the subducting Indo-Australian plate. It is one of the most seismogenic structures on Earth, being responsible for many great and giant earthquakes, including the 2004 Indian Ocean earthquake and tsunami that killed over 227,000 people. The Sunda megathrust can be divided into the Andaman Megathrust, Sumatra(n) Megathrust and Java(n) Megathrust. The Bali-Sumbawa segment is much less active and therefore does not have the "megathrust" term associated with it.
The 1861 Sumatra earthquake occurred on 16 February and was the last in a sequences of earthquakes that ruptured adjacent parts of the Sumatran segment of the Sunda megathrust. It caused a devastating tsunami which led to several thousand fatalities. The earthquake was felt as far away as the Malay peninsula and the eastern part of Java. The rupture area for the 2005 Nias–Simeulue earthquake is similar to that estimated for the 1861 event.
The 1996 Chimbote earthquake occurred on February 21 at 07:51 local time about 130 km off the coast of northern Peru, near the Peru–Chile Trench. The earthquake had a moment magnitude of 7.5 and occurred at 25.0 km (15.5 mi) depth.
The 1965 Oaxaca earthquake occurred in Mexico on August 23 at 13:46 with a moment magnitude of 7.5. Five people were reported dead in Mexico City and one in Oaxaca. There was an anomalous change in seismic activities before the earthquake. There was a quiescent stage from late 1963 to mid-1964, and it was followed by a renewal of seismic activities before the main shock. This earthquake was a shallow thrust earthquake in the interplate subduction zone, in which the Cocos Plate is subducting beneath the North American Plate.
The 1984 Northern Sumatra earthquake occurred with a moment magnitude of 7.2 on November 17 at 06:49 UTC. The epicentre was located off the coast of Sumatra, near the island of Nias, where building damage was reported. This earthquake could be strongly felt in parts of Northern Sumatra, including Padang and Medan. The focal mechanism corresponded to reverse faulting.
The 1935 Sumatra earthquake occurred at 09:35 local time on 28 December. It had a magnitude of Mw 7.7 and a maximum felt intensity of VII (Damaging) on the European macroseismic scale. It triggered a minor tsunami.
The 2002 Sumatra earthquake occurred at 01:26 UTC on 2 November. It had a magnitude of 7.4 on the moment magnitude scale with an epicenter just north of Simeulue island and caused three deaths. This earthquake is regarded as a foreshock of the 2004 Indian Ocean earthquake, which had an epicenter about 60 km to the northwest.
The 1959 Kamchatka earthquake occurred on May 4 at 19:15 local time with a moment magnitude of 8.0–8.3, and a surface wave magnitude of 8.25. The epicenter was near the Kamchatka Peninsula, Russian SFSR, USSR. Building damage was reported in Petropavlovsk-Kamchatsky. The maximum intensity was VIII (Damaging) on the Medvedev–Sponheuer–Karnik scale. The intensity in Petropavlovsk-Kamchatsky was about VIII MSK.
The 1746 Lima–Callao earthquake occurred at 22:30 local time on 28 October with a moment magnitude of 8.6–8.8 and a maximum Mercalli intensity of XI (Extreme). The epicenter was located about 90 km (56 mi) north-northwest of the capital Lima, which was almost completely destroyed, and the subsequent tsunami devastated the port city of Callao. It was the deadliest earthquake in Peru’s history prior to the 1970 earthquake.
The 1996 Nazca earthquake occurred on November 12 at 16:59 UTC. The earthquake was located offshore near Nazca, Peru. It has a magnitude of Mw 7.7. Fourteen people were reported dead. Four-thousand houses collapsed and 11,000 were partially damaged. Nazca and Acarí were the most affected cities. Liquefaction was observed in the bed of the Yauca River. The intensity was VIII (Severe) in Nazca. A tsunami was triggered by this earthquake. The recorded peak-to-trough heights of the tsunami were 25 cm in Callao, Peru and 35 cm in Arica, Chile.
The November 1960 Peru earthquake occurred offshore northern Peru on November 20 at 17:02 local time. The magnitude of the earthquake was Ms 6.75 by using the conventional surface-wave magnitude measurement within a shorter duration of ~20 s. However, there is a large discrepancy between the magnitudes in Ms and Mw in this earthquake. The discrepancy was caused from the earthquake's long source duration of about 130 s, and by calculating the seismic moment, the magnitude would be Mw 7.6 or Mw 7.8, according to different sources. This earthquake belongs to a category of earthquakes with slow rupture velocities and potential of producing tsunamis larger than those expected from the moment magnitudes.
The 1941 Andaman Islands earthquake struck the Andaman Islands on June 26 with a magnitude of 7.7 to 8.1. Details of this event are poorly known as much of Southeast Asia was in the turmoil of World War II. The quake caused severe damage in the Andaman Islands. The tsunami it triggered was reported along the Andaman and Nicobar Islands, India, and Sri Lanka. There may have been damage and deaths in Bangladesh, Myanmar, and Thailand due to the tsunami.
Flat slab subduction is characterized by a low subduction angle beyond the seismogenic layer and a resumption of normal subduction far from the trench. A slab refers to the subducting lower plate. A broader definition of flat slab subduction includes any shallowly dipping lower plate, as in western Mexico. Flat slab subduction is associated with the pinching out of the asthenosphere, an inland migration of arc magmatism, and an eventual cessation of arc magmatism. The coupling of the flat slab to the upper plate is thought to change the style of deformation occurring on the upper plate's surface and form basement-cored uplifts like the Rocky Mountains. The flat slab also may hydrate the lower continental lithosphere and be involved in the formation of economically important ore deposits. During the subduction, a flat slab itself may deform or buckle, causing sedimentary hiatus in marine sediments on the slab. The failure of a flat slab is associated with ignimbritic volcanism and the reverse migration of arc volcanism. Multiple working hypotheses about the cause of flat slabs are subduction of thick, buoyant oceanic crust (15–20 km) and trench rollback accompanying a rapidly overriding upper plate and enhanced trench suction. The west coast of South America has two of the largest flat slab subduction zones. Flat slab subduction is occurring at 10% of subduction zones.
The 1604 Arica earthquake is an earthquake that occurred at 1:30 pm on November 24, 1604, offshore Arica, Chile. The estimated magnitude range is 8.0–8.5 Ms and possibly up to 9.0 Mw. It had a destructive tsunami that destroyed Arica and caused major damage at Arequipa. 1,200 km of coastline were affected by the tsunami. The recorded effects of this earthquake are very similar to those for the 1868 Arica event, suggesting a similar magnitude and rupture area of the megathrust between the subducting Nazca Plate and the overriding South American Plate. Tsunami deposits have been identified on the Chatham Islands that are likely to have been caused by a trans-Pacific tsunami caused by the 1604 earthquake.
The earthquake cycle refers to the phenomenon that earthquakes repeatedly occur on the same fault as the result of continual stress accumulation and periodic stress release. Earthquake cycles can occur on a variety of faults including subduction zones and continental faults. Depending on the size of the earthquake, an earthquake cycle can last decades, centuries, or longer. The Parkfield portion of the San Andreas fault is a well-known example where similarly located M6.0 earthquakes have been instrumentally recorded every 30–40 years.
The 1979 Yapen earthquake occurred on September 12 at 05:17:51 UTC. It had an epicenter near the coast of Yapen Island in Irian Jaya, Indonesia. Measuring 7.5 on the moment magnitude scale and having a depth of 20 km (12 mi), it caused severe damage on the island. At least 115 were killed due to shaking and a moderate tsunami.