Earthquake swarm

Last updated
Matsushiro earthquake swarm (1965-1970) Matsushiro earthquake swarm.jpg
Matsushiro earthquake swarm (1965–1970)
Chronology of the 2003-2004 Ubaye earthquake swarm .mw-parser-output .hidden-begin{box-sizing:border-box;width:100%;padding:5px;border:none;font-size:95%}.mw-parser-output .hidden-title{font-weight:bold;line-height:1.6;text-align:left}.mw-parser-output .hidden-content{text-align:left} Complete caption Each red bar shows the number of earthquakes daily detected (left-handside scale). More than 16,000 earthquakes were detected within 2 years. White circles show the magnitude of ~1,400 earthquakes which could be located (right-handside magnitude scale). Sismalp (the local monitoring network) was not able to locate all events below magnitude 1, which explains why very-small-magnitude events are seemingly lacking. (According to the Gutenberg-Richter law, M0 events are approximately 10 times more numerous than M1 events.) HistoCrise.jpg
Chronology of the 2003–2004 Ubaye earthquake swarm
Complete caption
Each red bar shows the number of earthquakes daily detected (left-handside scale). More than 16,000 earthquakes were detected within 2 years. White circles show the magnitude of ~1,400 earthquakes which could be located (right-handside magnitude scale). Sismalp (the local monitoring network) was not able to locate all events below magnitude 1, which explains why very-small-magnitude events are seemingly lacking. (According to the Gutenberg–Richter law, M0 events are approximately 10 times more numerous than M1 events.)

In seismology, an earthquake swarm is a sequence of seismic events occurring in a local area within a relatively short period. The time span used to define a swarm varies, but may be days, months, or years. Such an energy release is different from the situation when a major earthquake (main shock) is followed by a series of aftershocks: in earthquake swarms, no single earthquake in the sequence is obviously the main shock. In particular, a cluster of aftershocks occurring after a mainshock is not a swarm. [2]

Contents

History and generalities

The Ore Mountains (Erzgebirge), which form the border between the Czech Republic and Germany, western Bohemia and the Vogtland region, have been known since the 16th century as being prone to frequent earthquake swarms, which typically last a few weeks to a few months. In 1899, Austrian geologist Josef Knett, while studying a swarm of about a hundred events felt in western Bohemia/Vogtland between January and February 1824, coined the noun Schwarmbeben, i.e. "swarm [earth]quake". [3] The term "swarm" comes from the fact that hypocentres give the impression of agglutinating like a bee swarm when plotted onto a map, a cross-section or a 3D model.[ citation needed ]

One of the best-documented swarms occurred near Matsushiro, a suburb of Nagano, to the north-west of Tokyo. The Matsushiro swarm lasted from 1965 to 1967 and generated about 1 million earthquakes. This swarm had the peculiarity of being sited just under a seismological observatory installed in 1947 in a decommissioned military tunnel. It began in August 1965 with three earthquakes too weak to be felt, but three months later, a hundred earthquakes could be felt daily. On 17 April 1966, the observatory counted 6,780 earthquakes, with 585 of them having a magnitude great enough to be felt, which means that an earthquake could be felt, on average, every two and a half minutes. [4] The phenomenon was clearly identified as linked to a magma uplift, perhaps initiated by the 1964 Niigata earthquake, which occurred the previous year. [5]

Earthquake swarms are common in volcanic regions such as Japan, Central Italy, the Afar depression or Iceland, where they occur before and during eruptions, but they are also observed in zones of Quaternary volcanism or of hydrothermal circulation, such as Vogtland/western Bohemia and the Vosges massif, and less frequently far from tectonic plate boundaries in locations such as Nevada, Oklahoma or Scotland. In all cases, high-pressure fluid migration in the Earth's crust seems to be the trigger mechanism and the driving process that govern the evolution of the swarm in space and time. [6] [7] The Hochstaufen earthquake swarm in Bavaria, with 2-km-deep foci, is one of the rare examples where an indisputable relationship between seismic activity and precipitation could be established. [8]

Earthquake swarms raise public-safety issues: first, because the end of seismic activity cannot be predicted; second, because it is uncertain whether another earthquake with a magnitude larger than those of previous shocks in the sequence will occur (the 2009 L'Aquila earthquake in Italy illustrates this, with an MW  6.3 shock following a swarm activity with magnitudes between 1 and 3). Even though swarms usually generate moderate shocks, the persistence of felt earthquakes can be disruptive and cause distress to the population.

Examples

The following examples were chosen for peculiarities of certain swarms (for instance: large number of events, complex interaction with larger shocks, long period of time, ultra-shallow focal depth), or because of their geographical region, some swarms occurring in otherwise aseismic regions. It is not intended to be a list of all the swarms happening worldwide.

Asia

India

  • Since 11 November 2018, an earthquake swarm has been observed in the region of Dahanu, Maharashtra, an otherwise aseismic area. Ten to twenty quakes are felt daily, with magnitudes usually smaller than 3.5 (maximum magnitude 4.1 in February 2019). Even with this low-level of magnitude, two shocks proved destructive and even lethal, probably because their foci were very shallow. [9]
  • Bamhori village in Seoni district is also experiencing regular earthquakes since February 2000.

Philippines

  • An earthquake swarm occurred from early April 2017 to mid August 2017 in the province of Batangas. Four shocks in the 5.5–6.3 magnitude range (2017 Batangas earthquakes) caused damage in southern Luzon; they occurred at the beginning of the swarm: Ms5.5 (4 April), Ms5.6 and Ms6.0 (8 April), and Ms6.3 (11 April). [10] The origin of the 3 first major quakes seems established since they had practically the same epicentre; they occurred within the crust (7–28-km depth range). However, the strongest and latest quake does not seem related to the swarm: its epicentre is 50 km away, and its focal depth is moreover very different (177 km, according to Phivolcs, the local seismic monitoring agency, a value which classifies this quake as an "intermediate-depth event"). This example shows how complex can be the interaction between a swarm and an independent earthquake, even though this last one is very likely to have been triggered by the swarm activity.
  • October 15, 2020, an earthquake swarm occurred on the island of Panay ranging from magnitudes 2.5-4.5. Most of these quakes felt in Iloilo City. [11] A previous swarm also hit Panay on November 5, 2018 (Including Antique, Iloilo and Guimaras) ranging from magnitudes 4.0-4.8. The first earthquake (magnitude 4.7) at 7:45 A.M, occurred at San Jose, Antique. Just a few minutes after, the second quake (magnitude 4.0) occurred at Sibunag, Guimaras. At 10:54 A.M, The third quake (magnitude 4.8) occurred at Guimbal, Iloilo. Intensity 4 was felt in Iloilo City [12]
  • A series of earthquakes that hit Mindanao in 2019 were classified as an earthquake swarm. [13]
    On October 16, a magnitude 6.3 (Mwp) Struck Tulunan cotabato (Epicenter of earthquake). Intensity VII was felt in Tulunan, M'lang, Makilala and Kidapawan City, Cotabato. Intensity VI was felt in Digos City, Davao del Sur; Santo Niño, South Cotabato and Tacurong City, Sultan Kudarat. [14] On October 29, a magnitude 6.6 (Mww) struck Tulunan again. At least ten deaths were reported and four hundred individuals were injured. [15] Intensity VII was recorded in Tulunan and Makilala; Kidapawan City; Digos City, Bansalan and Magsaysay, Davao del Sur and Malungon, Sarangani. Intensity VI was recorded in Koronadal City and Davao City. [16] Just 2 days after on October 31, an earthquake struck Tulunan again (Magnitude 6.5Mww) The death toll of two quakes was raised into 24 and 563 were injured. [17] Eva's Hotel in Kidapawan City collapsed during the quake [18]
  • On October 14-18 2021 an earthquake swarm occurred on Camarines Sur ranging from magnitudes 1.7-4.3 with the depth of 1–40 km. Some of these events were felt on Camarines Norte and Albay. PHIVOLCS recorded at least 27 earthquakes (10 were felt) in Camarines Sur. [19]

Europe

Iceland

  • A swarm of intense earthquakes in the Reykjanes Peninsula, Iceland began on 24 October 2023, due to a magmatic intrusion underneath the area. The frequency and intensity of the earthquakes dramatically increased 10 November, with 20,000 tremors recorded by that time, the largest of which exceeded magnitude 5.2. An evacuation was ordered in the town of Grindavík, which is located near the area of the seismic activity. Large-scale subsidence in and around the town is reported to have caused significant damage. [20] An earthquake swarm began on the evening of 24 October due to the magmatic intrusion, with the intensity of the earthquakes decreasing by 30 October. Approximately 8,000 earthquakes were detected; most of these tremors occurred at a depth of 2–4 km. The Icelandic Meteorological Office (IMO) reported that the swarm was focused around Svartsengi, north of Grindavík. About 700 earthquakes were recorded earlier in the month, the largest reaching magnitude 3.3.The largest of the earthquakes to date reached magnitude 5.1 on 10 November. By this time, over 22,000 earthquakes had been recorded since the beginning of the swarm in October. The IMO predicted that an eruption was likely, stating that "it will take several days (rather than hours) for magma to reach the surface." The greatest extent of the magma intrusion was inferred to be around the Sundhnúkur crater chain, approximately 3.5 km north of Grindavík. Instruments detected the presence of sulphur dioxide in the atmosphere on 14 November, indicating that magma was now only a few hundred metres under the surface. Although the number of earthquakes decreased somewhat since 10 November, the IMO was still recording between 700–1,000 earthquakes daily by 14 November. Ground deformation sensors at Festarfjall [ˈfɛstarˌfjatl̥] and Svartsengi recorded that the ground had moved apart by 120 centimetres. Satellite measurements recorded the subsidence by about one metre of a swathe of land measuring approximately five kilometers long and two kilometers wide, running from the Sundhnúkur craters to the western side of Grindavík. The creation of this graben-like formation has enabled scientists to estimate the volume of the magmatic intrusion as approximately 70 million cubic metres. It is estimated that the subsidence has been continuing at a rate of about four centimeters (1.6 inches) a day. A large crack opened up through the town, which old maps indicate is a reactivation of an existing fault. Scientists at the University of Iceland believe that the fault was created by the last Sundhnúkur eruption over 2,000 years ago. Sensors emplaced in a borehole in Svartsengi detected the presence of sulphur dioxide on 16 November, a classic signature of magma close to the surface. This has led the IMO to conclude that the area around the volcanic edifice of Hagafell, approximately 2 km north of Grindavík, is at the highest level of risk. A rapid 30 mm uplift of the ground in the Svartsengi area was recorded from 18-21 November, likely indicating an upwelling of magma from a source five or more kilometers below the ground. An eruption was still regarded as likely as of 21 November. [20]

Czech Republic / Germany

  • The western Bohemia/Vogtland region is the border area between the Czech Republic and Germany where earthquake swarms were first studied at the end of the 19th century. Swarm activity is recurrent there, sometimes with large maximum magnitudes, as for instance in 1908 (maximum magnitude 5.0), 1985–1986 (4.6), 2000 (3.2), or 2008 (3.8). This latter swarm occurred near Nový Kostel in October 2008 and lasted only 4 weeks, but up to 25,000 events were detected by WEBNET, the local monitoring network. The swarm is located on a steeply-dipping fault plane where an overall upward migration of activity was observed (first events at the bottom and last events at the top of the activated fault patch). [21]

France

Ubaye earthquake swarms Complete caption White: 2003-2004 swarm; pink: 2012-2015 swarm up to 2014-04-06; red: earthquakes as of 2014-04-07; pink and red lined up in white: epicentres of 2012-02-26 earthquake (M=4.3) and 2014-04-07 earthquake (M=4.8); brown: latest 20 earthquakes in July 2015, just before the map was drawn. Symbol size directly proportional to magnitude. Blue triangles show the 3 nearest seismic stations. Carte150728.jpg
Ubaye earthquake swarms
Complete caption
White: 2003–2004 swarm; pink: 2012–2015 swarm up to 2014-04-06; red: earthquakes as of 2014-04-07; pink and red lined up in white: epicentres of 2012-02-26 earthquake (M=4.3) and 2014-04-07 earthquake (M=4.8); brown: latest 20 earthquakes in July 2015, just before the map was drawn. Symbol size directly proportional to magnitude. Blue triangles show the 3 nearest seismic stations.
  • In Alpes-de-Haute-Provence, the Ubaye Valley is the most active seismic zone in the French Alps. Earthquakes can follow there the classical scheme "mainshock + aftershocks" (for instance the 1959 M5.5 earthquake, which caused heavy damage and two casualties). But seismic energy is principally released by swarms. This is particularly the case in the upper valley, between Barcelonnette and the French-Italian border. At the beginning of the 21st century, La Condamine-Châtelard experienced an exceptional swarm activity in an area where usually only a few low-magnitude events occur every year. A first swarm developed in 2003–2004 when more than 16,000 events were detected by the local monitoring network, but with magnitudes keeping to low values (2.7). On a map, the 2003–2004 swarm is 8-km long. After a period of almost complete inactivity, it was followed by a second swarm (2012–2014), slightly offset by a few kilometres, and with a length of 11 km. This second swarm was initiated by an M4.3 earthquake in February 2012. Another M4.8 earthquake in April 2014 reactivated the swarm in 2014–2015. These two major shocks, which caused damage in the nearby localities, were of course followed by their own short sequence of aftershocks, but such a 4-year activity for moderate magnitude shocks clearly characterizes a swarm. Most foci were located in the 4–11-km depth range, within the crystalline basement. Focal mechanisms involve normal faulting, but also strike-slip faulting. [1] [6]
  • In the lower Rhône Valley, the Tricastin has been known from the 18th century as the seat of earthquake swarms which sometimes caused damage, as in 1772–1773 and 1933–1936, and which were characterized by barrage-like detonations—at least so reported by the inhabitants. No seismic activity had been documented in the region since 1936, when a very weak swarm appeared for a few months in 2002–2003 (maximal magnitude 1.7). [22] Had their foci not been sited just under a hamlet in the vicinity of Clansayes, and very close to the surface (200 m deep), these shocks would have gone unnoticed. In such a scenario of "ultra-shallow" seismicity, even earthquakes of very low magnitude (1, or 0, or even negative magnitude) can be felt as explosions or water-hammer noises, more than as vibrations. [23] Most foci were located in an Upper-Cretaceous reef-limestone slab which bursts out periodically in the course of centuries for still unknown reasons for a few months or a few years. A 200-m focal depth is believed to be a worldwide record value for tectonic events.
  • In the French Alps, the Maurienne Valley is from time to time prone to earthquake swarms. During the 19th century, a protracted swarm lasted 5 years and a half, from December 1838 to June 1844. [24] Some earthquakes of the sequence caused damage in the region close to Saint-Jean-de-Maurienne, but this long swarm with many felt events made things particularly difficult for the population. More recently, a swarm appeared in October 2015 near Montgellafrey, in the lower part of the valley. [25] Its activity kept low until 17 October 2017, when more than 300 earthquakes occurred within a fortnight, with a maximal magnitude of 3.7 being reached twice in late October 2017. The seismic activity lasted another full year, thus yielding a duration of more than 3 years for the full swarm.

Central America

El Salvador

  • In April 2017, the Salvadoran municipality of Antiguo Cuscatlán, a suburb of San Salvador, experienced a sequence of close to 500 earthquakes within 2 days, with magnitudes in the 1.5–5.1 range. There was one casualty and minor damage due to the strongest quake. Local experts did not identify any anomalous activity at nearby volcanoes. [26]

North America

United States

  • Between February and November 2008, Nevada experienced a swarm of 1,000 low-magnitude quakes generally referred to as the 2008 Reno earthquakes. [27] The peak activity was in April 2008, when 3 quakes with magnitudes larger than 4 occurred within 2 days. The largest one registered a moment magnitude of 4.9 and caused damage in the immediate area around the epicenter.
  • The Yellowstone Caldera, a supervolcano in NW Wyoming, has experienced several strong earthquake swarms since the end of the 20th century. In 1985, more than 3,000 earthquakes were observed over a period of several months. More than 70 smaller swarms have been detected since. The United States Geological Survey states these swarms are likely caused by slips on pre-existing faults rather than by movements of magma or hydrothermal fluids. At the turn of the year 2008, more than 500 quakes were detected under the NW end of Yellowstone Lake over a seven-day span, with the largest registering a magnitude of 3.9. Another swarm started in January 2010, after the Haiti earthquake. With 1,620 small events in late January 2010, this swarm is the second-largest ever recorded in the Yellowstone Caldera. Interestingly, most of these swarms have "rapid-fire" characteristics: they seemingly appear out of nowhere and can churn out tens or hundreds of small to moderate quakes within a very short time frame. Such swarms usually occur within the caldera boundary, as was especially the case in 2018. [28]
Guy-Greenbrier earthquake swarm: map of epicentres for the period 2010-08-06 to 2011-03-01. Arkansas swarm.png
Guy-Greenbrier earthquake swarm: map of epicentres for the period 2010-08-06 to 2011-03-01.
  • The Guy-Greenbrier earthquake swarm occurred in central Arkansas beginning in August 2010. Epicentres show a linear distribution, with a clear overall shift in activity towards the southwest with time, and a magnitude of 4.7 was computed for the largest event. Analysis of the swarm has suggested a link with deep waste disposal drilling. It has led to a moratorium on such drilling. [30]
  • On 2 September 2017, an earthquake swarm appeared around Soda Springs, Idaho. Five quakes with magnitudes between 4.6 and 5.3 occurred within 9 days. Keeping the 2009 L'Aquila case in mind, and because Idaho had experienced an M6.9 earthquake in 1983, experts warned residents that a stronger quake could follow (an unlikely but still possible scenario for them). [31]
  • From early 2016 to late 2019, a swarm of earthquakes occurred near Cahuilla in Riverside County, California. More than 22,000 individual seismic events were recorded—ranging in magnitude from 0.7 to 4.4 -- the strongest one occurred in August 2018, south of Lake Riverside, just off Cahuilla Road (SR 371). By using computer algorithms and machine learning, researchers were able to infer the following detailed picture of the Cahuilla fault zone responsible for the earthquake swarm. The fault zone is no more than 50 m (160 ft) wide, 4 km (2.5 mi) long, with the earliest seismic swarm events localized down near its base at 9 km (5.6 mi) below the surface and the latest events migrating upwards to 5 km (3.1 mi) below the surface and spreading throughout the fault zone's length. Containing complex subterranean horizontal channels and prominent bents in its depth profile, the fault zone sits on top of a deeper natural underground reservoir of fluid under pressure with a connector at 8 km (5.0 mi) below the surface that was initially sealed off from the fault zone. When that seal broke open in early 2016, fluids were injected up into the fault zone's base and diffused slowly through the complex channels up to 5 km (3.1 mi) below the surface, which triggered the prolonged earthquake swarm that lasted until late 2019. This analysis provides detailed evidence that fault zone valving is a mechanism for seismogenesis in swarms. [32] [33]

Atlantic Ocean

Indian Ocean

Pacific Ocean

See also

Related Research Articles

<span class="mw-page-title-main">Earthquake</span> Sudden movement of the Earths crust

An earthquake – also called a quake, tremor, or temblor – is the shaking of the surface of Earth resulting from a sudden release of energy in the 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.

<span class="mw-page-title-main">Yellowstone Caldera</span> Volcanic caldera in Yellowstone National Park in the United states

The Yellowstone Caldera, sometimes referred to as the Yellowstone Supervolcano, is a volcanic caldera and supervolcano in Yellowstone National Park in the Western United States. The caldera and most of the park are located in the northwest corner of Wyoming. The caldera measures 43 by 28 miles, and postcaldera lavas spill out a significant distance beyond the caldera proper.

<span class="mw-page-title-main">New Madrid Seismic Zone</span> Major seismic zone in the southern and midwestern United States

The New Madrid Seismic Zone, 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.

A volcano tectonic earthquake or volcano earthquake is caused by the movement of magma beneath the surface of the Earth. The movement results in pressure changes where the rock around the magma has experienced stress. At some point, this stress can cause the rock to break or move. This seismic activity is used by scientists to monitor volcanoes. The earthquakes may also be related to dike intrusion or occur as earthquake swarms.

The 2006 Gulf of Mexico earthquake occurred in the eastern Gulf of Mexico on September 10 at 10:56 AM Eastern Daylight Time. The intraplate earthquake measured 5.9 on the moment magnitude scale and its epicenter was located about 250 miles (400 km) west-southwest of Anna Maria, Florida. The event was felt throughout much of the Gulf Coast of the United States and was the second earthquake of magnitude 5 or greater in the Gulf during 2006. Felt intensities, as measured on the Mercalli intensity scale, were as high as IV (Light) in Florida, with parts of Georgia at III (Weak).

<span class="mw-page-title-main">1976 Moro Gulf earthquake</span> Earthquake in the Philippines

The 1976 Moro Gulf earthquake and tsunami occurred on August 17, 1976, at 00:11 local time near the islands of Mindanao and Sulu, in the Philippines. It measured 8.0 on the moment magnitude scale occurring at a depth of 20 km (12 mi). The earthquake was accompanied by a destructive tsunami that resulted in a majority of the estimated 5,000 to 8,000 fatalities. It was the deadliest and strongest earthquake in the Philippines in 58 years since the 1918 Celebes Sea earthquake.

Earthquakes have occurred in Western Australia (WA) on a regular basis throughout its geological history.

A series of small volcanic earthquakes measuring less than 4.0 on the Richter magnitude scale took place in the sparsely populated Nazko area of the Central Interior of British Columbia, Canada, from October 9, 2007, to June 12, 2008. They occurred just west of Nazko Cone, a small tree-covered cinder cone that last erupted about 7,200 years ago.

This is a list of different types of earthquake.

The 1993 Klamath Falls earthquakes took place in Klamath Falls, Oregon, beginning on Monday, 20 September at 8:28 p.m. The doublet earthquake registered respective magnitudes of 6.0 and 5.9 on the moment magnitude scale. The earthquakes were located at a depth of 5.6 miles (9 km) and tremors continued to be felt more than three months after the initial shocks.

<span class="mw-page-title-main">Geological deformation of Iceland</span>

The geological deformation of Iceland is the way that the rocks of the island of Iceland are changing due to tectonic forces. The geological deformation explains the location of earthquakes, volcanoes, fissures, and the shape of the island. Iceland is the largest landmass (102,775 km²) situated on an oceanic ridge. It is an elevated plateau of the sea floor, situated at the crossing of the Mid-Atlantic Ridge and the Greenland-Iceland-Faeroe Ridge. It lies along the oceanic divergent plate boundary of North American Plate and Eurasian Plate. The western part of Iceland sits on the North American Plate and the eastern part sits on the Eurasian Plate. The Reykjanes Ridge of the Mid-Atlantic ridge system in this region crosses the island from southwest and connects to the Kolbeinsey Ridge in the northeast.

<span class="mw-page-title-main">2018 Hawaii earthquake</span> 6.9-magnitude earthquake in Hawaii

On May 4, 2018, an earthquake with a magnitude of Mw 6.9 struck Hawaii island in the Hawaii archipelago at around 12:33 p.m. local time. The earthquake's epicenter was near the south flank of Kīlauea, which has been the site of seismic and volcanic activity since late April of that year. According to the United States Geological Survey the quake was related to the new lava outbreaks at the volcano, and it resulted in the Hilina Slump moving about two feet. It was the largest earthquake to affect Hawaii since the 1975 earthquake, which affected the same region, killing two people and injuring another 28.

<span class="mw-page-title-main">Geology of Mayotte</span>

As part of the Comoro Islands chain in the Mozambique Channel, the geology of Mayotte is virtually the same as the geology of the Comoros, the rest of the island chain which is independent of France. The island resulted from the rifting of Madagascar away from Africa as well as "hotspot" mantle plume activity, and is also impacted by seismicity and deformation associated with the East African Rift. However, because Mayotte is a part of France its geology is significantly more researched than that of other islands in the chain.

<span class="mw-page-title-main">11 November 2018 Mayotte seismic event</span>

The 11 November 2018 Mayotte seismic event is a seismic event of unknown origin that occurred about 24 kilometres (15 mi) off the coast of Mayotte, an overseas department and region of France in the Indian Ocean. It was recorded by seismograms globally, including in Kenya, Chile, New Zealand, Canada, and Hawaii, almost 18,000 kilometres (11,000 mi) away. Despite this, no one felt it. The seismic waves lasted for over 20 minutes. Most earthquakes have P waves and S waves, which are later followed by long-period surface waves. The Mayotte event lacked P waves and S waves, but did cause a long-period surface wave travelling at 14,000 km/h (9,000 mph) around the globe. Additionally, the signal released by the earthquake resembled a clean sine wave, while most earthquake waves have multiple frequencies.

The 2019 Ridgecrest earthquakes of July 4 and 5 occurred north and northeast of the town of Ridgecrest, California located in Kern County and west of Searles Valley. They included three initial main shocks of Mw magnitudes 6.4, 5.4, and 7.1, and many perceptible aftershocks, mainly within the area of the Naval Air Weapons Station China Lake. Eleven months later, a Mw  5.5 aftershock took place to the east of Ridgecrest. The first main shock occurred on Thursday, July 4 at 10:33 a.m. PDT, approximately 18 km (11.2 mi) ENE of Ridgecrest, and 13 km (8.1 mi) WSW of Trona, on a previously unnoticed NE-SW trending fault where it intersects the NW-SE trending Little Lake Fault Zone. This quake was preceded by several smaller earthquakes, and was followed by more than 1,400 detected aftershocks. The M 5.4 and M 7.1 quakes struck on Friday, July 5 at 4:08 a.m. and 8:19 p.m. PDT approximately 10 km (6 miles) to the northwest. The latter, now considered the mainshock, was the most powerful earthquake to occur in the state in 20 years. Subsequent aftershocks extended approximately 50 km (~30 miles) along the Little Lake Fault Zone.

The 2019 Cotabato earthquakes were an earthquake swarm which struck the province of Cotabato on the island of Mindanao in the Philippines in October 2019. Three of these earthquakes were above 6.0 on the moment magnitude scale with a Mercalli intensity of VIII. More than 40 people have been reported dead or missing and nearly 800 were injured as a result of these events.

An earthquake struck near the Hawaiian island of Lanai on February 19, at 10:11 pm HST with an estimated magnitude of 7.5 on the moment magnitude scale (Mw ). It remains one of the largest seismic event to hit the Hawaiian Islands since the 1868 Ka‘ū earthquake, with its effects being felt throughout the entire archipelago. It caused severe damage on the islands of Lanai, Molokai and Maui. A tsunami may have been generated however there are speculations if it had actually happened. Despite the size of the quake and the extent of damage, there were no deaths.

<span class="mw-page-title-main">2021 Chignik earthquake</span> 7th largest earthquake in the US

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.

On 9 July 2019, at 8:36 PM (PST), an earthquake measuring Mw 5.6 jolted the province of North Cotabato, Davao del Sur, and other nearby provinces. The National Disaster Risk Reduction and Management Council reported one dead and three injured in Makilala after the earthquake, and a total of 164 families affected in Cotabato Province. Near the epicenter of the earthquake, the severity of strong ground motion was assigned VI (Strong) on the Modified Mercalli intensity scale. A total of 106 schools, 119 houses, and 14 other infrastructures were damaged by the earthquake.

References

  1. 1 2 Jenatton, Liliane; Guiguet, Robert; Thouvenot, François; Daix, Nicolas (2007). "The 16,000-event 2003-2004 earthquake swarm in Ubaye (French Alps)". J. Geophys. Res. 112 (B11): 304. Bibcode:2007JGRB..11211304J. doi: 10.1029/2006JB004878 . S2CID   129318590.
  2. ↑ Horálek, Josef; Fischer, Tomáš; Einarsson, Páll; Jakobsdótir, Steinunn (2015). "Earthquake swarms". In Beer, Michael; Kougioumtzoglou, Ioannis; Patelli, Eduardo; Au, Siu-Kui (eds.). Encyclopedia of Earthquake Engineering. Berlin: Springer. pp. 871–885. doi:10.1007/978-3-642-35344-4. ISBN   978-3-642-35343-7.
  3. ↑ Knett, Josef (1899). "Das Erzgebirgische Schwarmbeben zu Hartenberg vom 1. Jänner bis Feber 1824". Sitzungsber. Deutsch. Naturwiss.-Med. Ver. Böhmen (in German). 19: 167–191.
  4. ↑ "Matsushiro earthquake swarm". www.data.jma.go.jp. Retrieved 2017-10-31.
  5. ↑ Mogi, Kiyoo (1989). "The mechanics of the occurrence of the Matsushiro earthquake swarm in central Japan and its relation to the 1964 Niigata earthquake". Tectonophysics. 159 (1–2): 109–119. Bibcode:1989Tectp.159..109M. doi:10.1016/0040-1951(89)90173-X.
  6. 1 2 3 Thouvenot, François; Jenatton, Liliane; Scafidi, Davide; Turino, Chiara; Potin, Bertrand; Ferretti, Gabriele (2016). "Encore Ubaye: Earthquake swarms, foreshocks, and aftershocks in the southern French Alps". Bull. Seismol. Soc. Am. 106 (5): 2244–2257. Bibcode:2016BuSSA.106.2244T. doi:10.1785/0120150249.
  7. ↑ Špičák, Aleš (2000). "Earthquake swarms and accompanying phenomena in intraplate regions: a review". Studia Geophysica et Geodaetica. 44 (2): 89–106. doi:10.1023/A:1022146422444. S2CID   126768561.
  8. ↑ Kraft, Toni; Wassermann, Joachim; Schmedes, Eberhard; Igel, Heiner (2006). "Meteorological triggering of earthquake swarms at Mt. Hochstaufen, SE-Germany". Tectonophysics. 424 (3): 245–258. Bibcode:2006Tectp.424..245K. doi:10.1016/j.tecto.2006.03.044.
  9. ↑ Nair, Sandhya (2019-07-26). "Earthquake leads to roof crash, man killed in Dahanu". timesofindia.indiatimes.com. Retrieved 2019-09-04.
  10. ↑ Gamil, Jaymee (2017-04-08). "Batangas tremors part of 'earthquake swarm,' says Phivolcs". newsinfo.inquirer.net. Retrieved 2019-09-04.
  11. ↑ Quake ‘swarm’ hits Iloilo, Antique panaynews.net October 17, 2020
  12. ↑ Series of earthquakes hit parts of Panay island Monday cnnphilippines.com Published Nov 6, 2018 1:05:01 AM
  13. ↑ Cruz, Divina Nova Joy Dela (2019-11-01). "Quake 'swarm' hits Mindanao". The Manila Times. Retrieved 2022-09-27.
  14. ↑ "Earthquake Information – 16 Oct 2019 – 07:37:04 PM". PHIVOLCS. Archived from the original on December 2, 2019. Retrieved October 16, 2019.
  15. ↑ National Disaster Risk Reduction and Management Council (2 November 2019). "NDRRMC Update: SitRep No. 08 regarding Magnitude 6.6 and 6.5 Earthquakes in Tulunan, Nurth Cotabato" (PDF). Retrieved 2 November 2019.
  16. ↑ 1. "Earthquake Information – 29 Oct 2019 – 09:04:43 AM". PHIVOLCS. Archived from the original on October 31, 2019. Retrieved October 29, 2019.
  17. ↑ National Disaster Risk Reduction and Management Council (November 20, 2019). "NDRRMC Update: SitRep No. 30 regarding Magnitude 6.6 and 6.5 Earthquakes in Tulunan, North Cotabato" (PDF). Retrieved November 20, 2019.
  18. ↑ "Kidapawan hotel nearly collapses after magnitude 6.5 quake, several injured". ABS-CBN News. October 31, 2019. Retrieved November 4, 2019.
  19. ↑ "Series of tremors in CamSur considered as 'earthquake swarm' -- Phivolcs". Manila Bulletin. 2021-10-18. Retrieved 2022-09-16.
  20. 1 2 "2023 Iceland earthquakes", Wikipedia, 2023-11-24, retrieved 2023-11-24
  21. ↑ Fischer, Tomáš; Horálek, Josef; Michálek, Jan; Boušková, Alena (2010). "The 2008 West Bohemia earthquake swarm in the light of the WEBNET network" (PDF). J. Seismol. 14 (4): 662–682. Bibcode:2010JSeis..14..665F. doi:10.1007/s10950-010-9189-4. S2CID   140621431.
  22. ↑ Thouvenot, François; Jenatton, Liliane; Gratier, Jean-Pierre (2009). "200-m-deep earthquake swarm in Tricastin (lower Rhône Valley, France) accounts for noisy seismicity over past centuries". Terra Nova. 21 (3): 203–210. Bibcode:2009TeNov..21..203T. doi: 10.1111/j.1365-3121.2009.00875.x . S2CID   129836213.
  23. ↑ Thouvenot, François; Bouchon, Michel (2008). "What is the Lowest Magnitude Threshold at Which an Earthquake can be Felt or Heard, or Objects Thrown into the Air?". In Fréchet, Julien; Meghraoui, Mustapha; Stucchi, Massimiliano (eds.). Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes. Modern Approaches in Solid Earth Sciences. Vol. 2. Dordrecht: Springer. pp. 313–326. doi:10.1007/978-1-4020-8222-1_15. ISBN   978-1-4020-8221-4.
  24. ↑ Rothé, Jean-Pierre (1941). "La séismicité des Alpes occidentales". Ann. Inst. Phys. Globe (in French). III: 26–105.
  25. ↑ "Un séisme de faible magnitude enregistré en Maurienne". www.ledauphine.com. Retrieved 2017-11-15.
  26. ↑ Blašković, Teo (2017-04-11). "Powerful earthquake swarm under Metropolitan Area of San Salvador, El Salvador". watchers.news. Retrieved 2019-09-04.
  27. ↑ "Complex Behavior of a Nevada Earthquake Swarm". earthquakes.berkeley.edu. Retrieved 2019-09-03.
  28. ↑ "Rapid Energetic Swarms near West Thumb Lake, Yellowstone". www.monitorseis.net. Archived from the original on 2019-06-17. Retrieved 2019-09-03.
  29. ↑ Peterson, Mark D.; Mueller, Charles S.; Moschetti, Morgan P.; Hoover, Susan M.; Rubinstein, Justin L.; Llenos, Andrea L.; Michael, Andrew J.; Ellsworth, William L.; McGarr, Arthur F.; Holland, Austin A.; Anderson, John G. (2015). Incorporating Induced Seismicity in the 2014 United States National Seismic Hazard Model—Results of 2014 Workshop and Sensitivity Studies (USGS Open-File Report 2015–1070) (PDF) (Report). United States Geological Survey. p. 69. doi: 10.3133/ofr20151070 . ISSN   2331-1258. OCLC   38116130 . Retrieved 2019-09-04.
  30. ↑ Short, Louis (2011-06-24). "Permanent injection well moratorium proposed". The Sun Times. Archived from the original on 2011-06-30. Retrieved 2011-07-03.
  31. ↑ "M5.3 2017 Soda Springs, Idaho Sequence". earthquake.usgs.gov. Retrieved 2019-09-03.
  32. ↑ "Natural Fluid Injections Triggered Cahuilla Earthquake Swarm". caltech.edu. June 18, 2020. Retrieved 20 June 2020.
  33. ↑ Ross, Zachary E.; Cochran, Elizabeth S.; Trugman, Daniel T.; Smith, Jonathan D. (19 Jun 2020). "3D fault architecture controls the dynamism of earthquake swarms". Science. 368 (6497): 1357–1361. Bibcode:2020Sci...368.1357R. doi:10.1126/science.abb0779. OSTI   1739984. PMID   32554593. S2CID   219843436.
  34. ↑ Bernardo Marin; R. Mendez (2011-10-11). "La erupción volcánica submarina de El Hierro libera magma y gases en el océano". El País (in Spanish). Retrieved 2012-05-07.
  35. ↑ "Essaim de séismes à Mayotte : points de situation". www.brgm.fr (in French). Retrieved 2019-09-05.
  36. 1 2 "Volcan sous-marin au large de Mayotte, retour sur une découverte exceptionnelle". www.ipgp.fr (in French). Retrieved 2019-09-05.
  37. ↑ Lemoine, Anne; Briole, Pierre; Bertil, Didier; Roullé, Agathe; Foumelis, Michael; Thinon, Isabelle; Raucoules, Daniel; de Michele, Marcello; Valty, Pierre; Hoste Colomer, Roser (2020). "The 2018–2019 seismo-volcanic crisis east of Mayotte, Comoros islands: seismicity and ground deformation markers of an exceptional submarine eruption". Geophysical Journal International. 223 (1): 22–44. doi: 10.1093/gji/ggaa273 .
  38. ↑ Cesca, Simone; Letort, Jean; Razafindrakoto, Hoby N. T.; Heimann, Sebastian; Rivalta, Eleonora; Isken, Marius P.; Nikkhoo, Mehdi; Passarelli, Luigi; Petersen, Gesa M.; Cotton, Fabrice; Dahm, Torsten (2020). "Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation". Nature Geoscience. 13 (1): 87–93. Bibcode:2020NatGe..13...87C. doi:10.1038/s41561-019-0505-5. hdl: 10754/661261 . S2CID   209897160.
  39. ↑ Maya Wei-Haas (2018-11-28). "Strange waves rippled around the world, and nobody knows why". National Geographic . Archived from the original on November 28, 2018. Retrieved 2018-11-30.
  40. ↑ "Earthquake of magnitude 7.9 in the Santa Cruz Islands on 6 February 2013". CEA/DAM. Retrieved 2019-09-05.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.