An earthquake – also called a quake, tremor, or temblor – is the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak 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 New Madrid Seismic Zone (NMSZ), sometimes called the New Madrid Fault Line, is a major seismic zone and a prolific source of intraplate earthquakes in the Southern and Midwestern United States, stretching to the southwest from New Madrid, Missouri.
An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years.
The Cascadia subduction zone is a 960 km (600 mi) fault at a convergent plate boundary, about 110–160 km (70–100 mi) off the Pacific coast, that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is capable of producing 9.0+ magnitude earthquakes and tsunamis that could reach 30 m (98 ft). The Oregon Department of Emergency Management estimates shaking would last 5–7 minutes along the coast, with strength and intensity decreasing further from the epicenter. It is a very long, sloping subduction zone where the Explorer, Juan de Fuca, and Gorda plates move to the east and slide below the much larger mostly continental North American Plate. The zone varies in width and lies offshore beginning near Cape Mendocino, Northern California, passing through Oregon and Washington, and terminating at about Vancouver Island in British Columbia.
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 include most of the Earth's largest earthquakes.
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 Okhotsk microplate is a proposed minor tectonic plate covering the Kamchatka Peninsula, Magadan Oblast, and Sakhalin Island of Russia; Hokkaido, Kantō and Tōhoku regions of Japan; the Sea of Okhotsk, as well as the disputed Kuril Islands.
The Philippine Trench is a submarine trench to the east of the Philippines. The trench is located in the Philippine sea of the western North Pacific Ocean and continues NNW-SSE. It has a length of approximately 1,320 kilometres and a width of about 30 km (19 mi) from the center of the Philippine island of Luzon trending southeast to the northern Maluku island of Halmahera in Indonesia. At its deepest point, the trench reaches 10,540 meters.
Episodic tremor and slip (ETS) is a seismological phenomenon observed in some subduction zones that is characterized by non-earthquake seismic rumbling, or tremor, and slow slip along the plate interface. Slow slip events are distinguished from earthquakes by their propagation speed and focus. In slow slip events, there is an apparent reversal of crustal motion, although the fault motion remains consistent with the direction of subduction. ETS events themselves are imperceptible to human beings and do not cause damage.
This is a list of different types of earthquake.
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 7.2, or 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 2013 Solomon Islands earthquake struck Temotu Province within Solomon Islands on 6 February with a moment magnitude of 8.0 and a maximum Mercalli intensity of VIII (Severe). The epicentre was close to the Santa Cruz Islands within Temotu Province at the boundaries of the Indo-Australian and Pacific tectonic plates, causing local evacuations, a tsunami of 11 m (36 ft) and killing at least ten people.
The 1999 Ambrym earthquake occurred on November 26 at with a moment magnitude of 7.4 and a maximum Mercalli intensity of VII. The back arc thrust event occurred within the Vanuatu archipelago, just to the south of the volcanic island of Ambrym. Vanuatu, which was previously known as New Hebrides, is subject to volcanic and earthquake activity because it lies on an active and destructive plate boundary called the New Hebrides Subduction Zone. While the National Geophysical Data Center classified the total damage as moderate, a destructive local tsunami did result in some deaths, with at least five killed and up to 100 injured.
The 1965 Valparaíso earthquake struck near La Ligua in Valparaíso Region, Chile, about 140 km (87 mi) from the capital Santiago on Sunday, March 28 at 12:33 local time. The moment magnitude (Mw ) 7.4–7.6 earthquake killed 400–500 people and inflicted US$1 billion in damage. Many deaths were from El Cobre, a mining location that was wiped out after a series of dam failures caused by the earthquake spilled mineral waste onto the area, burying hundreds of residents. The shock was felt throughout the country and along the Atlantic coast of Argentina.
On the morning of January 5, 1699, a violent earthquake rocked the then Dutch East Indies city of Batavia on the island of Java, now known as the Indonesian capital city of Jakarta. Dutch accounts of the event described the earthquake as being "so heavy and strong" and beyond comparable to other known earthquakes. This event was so large that it was felt throughout west Java, and southern Sumatra.
An earthquake occurred off the coast of the Alaska Peninsula on July 28, 2021, at 10:15 p.m. local time. The large megathrust earthquake had a moment magnitude of 8.2 according to the United States Geological Survey (USGS). A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled. The mainshock was followed by a number of aftershocks, including three that were of magnitude 5.9, 6.1 and 6.9 respectively.
The 1979 Petatlán earthquake, also known as the IBERO earthquake occurred on March 14 at 05:07 local time in the Mexican state of Guerrero. The earthquake had a surface wave magnitude of Ms 7.6 or moment magnitude of Mw 7.4 and maximum Modified Mercalli intensity of VIII (Severe). The epicenter, onshore, was located 12 km south southeast of Vallecitos de Zaragoza.
In the early morning hours of Friday 24 December 2004, a moment magnitude 8.1 earthquake struck a remote area of the southern Tasman Sea. Its epicentre was located roughly 360 km (224 mi) northwest of the Auckland Islands of New Zealand, and roughly 600 km (373 mi) north of Macquarie Island of Australia. Shaking was reportedly felt as far as Tasmania and the South Island. The event was a complex intraplate earthquake within the Australian Plate, which generated a small tsunami.
The 1867 Central Java earthquake occurred on June 10 at between 04:20 and 04:30 local time. It struck off the southern coast of the Indonesian island with an estimated moment magnitude of 7.8 (Mw ). Widespread devastation occurred in Central Java, where as many as 700 people were killed. The intermediate-depth intraslab earthquake did not cause a tsunami.
