International Seismological Centre

Last updated

International Seismological Centre
Formation1964
Director
Dmitry Storchak
Staff
20 (2018)
Website http://www.isc.ac.uk/

The International Seismological Centre (ISC) is a non-governmental, nonprofit organisation charged with the final collection, definitive analysis and publication of global seismicity. [1] The ISC was formed in 1964 as an international organisation independent of national governments that would carry on the work of the International Seismological Summary in collecting and analyzing seismic data from around the world, and particularly to handle increased flow of data from the World-Wide Standard Seismograph Network (WWSSN), also established that year. [2] The ISC considers its prime task to be the collection and re-analysis of all available earthquake seismic date in order to produce definitive data on earthquakes. [3] The ISC's catalog is considered "the most complete and authoritative final depository of global earthquake parameter data." [4]

Contents

Purpose

The main scientific goal of the Centre is the definitive compilation of earthquake information and the readings on which they are based. Collection of reports of earthquake effects is also an important part of its operation and the Centre recomputes the location and occurrence time of earthquakes worldwide, making use of all available information.

Since 1957 the manipulation of the large volume of data has been mainly carried out by computer. Up until then ISS locations were determined manually with the help of a large globe. The ISC now uses a network of workstations accessing a relational database of nearly 50 Gbytes of online data.

The analysis of the earthquake data is undertaken in monthly batches and begins after at least 18 months to allow the information used to be as complete as possible. Although much of the work would be impossible without the Centre's large suite of computer programs, the final editing of events large enough to be detected by several independently operated networks is always carried out by seismologists who scrutinise the output for unlikely events and chance misassociation of readings.

During analysis the computer program first groups origin estimates from different agencies and then associates the individual station readings with the most likely event. In a typical month more than 200,000 station readings are analysed leading to an average of 10,000 events per month being identified, of which some 4,000 require manual review. Misassociations and other discrepancies are rectified and the remaining unassociated readings are searched for new events and previously unreported earthquakes are added to the database. The total number of events listed each month is several times greater than those obtained by any other worldwide location service and results from ISC's goal to provide a fully comprehensive list.

Data products

The data the ISC collects and processes forms the basis of several data products.

ISC Bulletin

The On-line Bulletin (a printed summary is available for a fee) is the main collection of ISC data, organised by events. After approximately two years all of the data collected for an event is reviewed and the hypocenters and magnitudes recalculated; the Reviewed Bulletin is "regarded as the definitive record of the Earth's seismicity." [5] Most of the other data products are subsets of the Bulletin.

ISC-EHB Bulletin

The original EHB Bulletin contains events from 1960 to 2008 (prior to adoption of a newer location algorithm) whose hypocentres were recalculated by the algorithm of Engdahl, van der Hilst & Buland (1998). This has been replaced by the ISC-EHB Bulletin, which extends the catalog to 2013.

ISC-GEM Catalogue

The ISC-GEM Global Instrumental Earthquake Catalogue (1900-2013) (prepared at the request of the GEM Foundation) catalogs magnitude 5.5 or greater earthquakes suitable for modeling and assessing seismic hazard and risk. Epicentral locations and hypocentral depths were recalculated from original travel time data using a consistent velocity model. Magnitudes are expressed as moment magnitude scale (Mw), taken either from reliable published values of seismic moment or from recalculated values of surface wave or body wave magnitude, converted to Mw using empirical relationships. [6]

IASPEI Ground Truth (GT) reference events

The IASPEI reference events database contains 9280 earthquakes and explosions whose hypocenters have been located within 10 km or less, often in conjunction with on-site studies ("ground truth"). These events have seen selected to better "see" the Earth's structure, and to provide references to which seismic networks can be more accurately calibrated.

Event Bibliography

The Event Bibliography catalogs scientific papers (mainly in English) that specifically discuss over 14,000 events. A valuable listing of papers that avoids problems inherent in most search services of variant place names or spellings, or trivial mentions.

History

List of directors

Publisher of the "Shide Circular Reports on Earthquakes"

Publisher of "Reports on Large Earthquakes"

Director of the International Seismological Summary

Director of International Seismological Centre

  • 1964–1970 P.L. Willmore
  • 1970–1977 E.P. Arnold
  • 1977–1997 A.A. Hughes
  • 1998–2003 R.J. Willeman
  • 2004–2007 A. Shapira
  • 2008–present D.A. Storchak

Notes

  1. Di Giacomo et al. 2014 , p. 354; Johnston & Halchuk 1993 , p. 134.
  2. Adams 2010; Musson 2013 , pp. 831–833.
  3. Adams & Richardson 1996 , p. 193.
  4. Yadav et al. 2009 , p. 610. In a 2008 document the U.S. Geological Survey said "it is because of the ISC's authoritative role that the USGS continues to refer to its final bulletin publication as 'preliminary'.
  5. "Bulletin of the International Seismological Centre" .
  6. "Overview of the ISC-GEM Catalogue" . Retrieved 30 November 2014.

Sources

  • Musson, R. M. W. (2013), "A history of British seismology", Bulletin of Earthquake Engineering, 11: 715–861, doi: 10.1007/s10518-013-9444-5 .

Related Research Articles

The 1978 Tabas earthquake occurred on September 16 at 19:05:55 local time in central Iran. The shock measured 7.4 on the moment magnitude scale and had a maximum Mercalli intensity of IX+ (Violent). The death toll was in the range of 15,000–25,000, with severe damage occurring in the town of Tabas.

The 1938 Banda Sea earthquake occurred on February 2 with an estimated magnitude of 8.5–8.6 on the moment magnitude scale and a Rossi–Forel intensity of VII. This oblique-slip event generated destructive tsunamis of up to 1.5 metres in the Banda Sea region, but there were no deaths.

The 1976 Songpan–Pingwu earthquake that struck Songpan and Pingwu counties in Sichuan, China consisted of three mainshocks on the 16th, 21st, and 23rd (UTC) of August. A 1984 report gave the magnitudes as 7.2, 6.7, and 7.2, respectively. The magnitudes were subsequently recalculated as 6.7, 6.3, and 6.4 on the Mw scale, and 7.0, 6.6, and 6.7 on the Ms scale. These were preceded by an earthquake swarm lasting three years. During the period from August 16 to August 31 there were over 400 aftershocks of magnitude 3.0 or greater.

<span class="mw-page-title-main">2008 Iceland earthquake</span> 2008 earthquake centered in southwestern Iceland

The 2008 Iceland earthquake was a doublet earthquake that struck on May 29 at 15:46 UTC in southwestern Iceland. The recorded magnitudes of the two main quakes were 5.9 Mw and 5.8 Mw , respectively, giving a composite magnitude of 6.1 Mw . There were no human fatalities, but 30 injuries were reported and a number of sheep were killed. The epicenter of the earthquake was between the towns of Hveragerði and Selfoss, about 45 kilometers (28 mi) east-southeast of the capital, Reykjavík. It was the strongest earthquake to hit Iceland since the summer of 2000.

<span class="mw-page-title-main">2009 Papua earthquakes</span> Earthquake in Papua, Indonesia

The 2009 Papua earthquakes occurred on January 4 local time in Indonesia's West Papua province. The very large earthquake doublet comprised a Mw 7.6 initial shock that had a maximum Mercalli intensity of VI (Strong) and a second event measuring Mw  7.4 and a maximum Mercalli intensity of VII. The events took place less than three hours apart to the east-northeast of Sorong on the Bird's Head Peninsula and left at least four people dead and dozens injured.

The 1988 Nepal earthquake occurred in Nepal near the Indian border and affected much of northern Bihar. The magnitude 6.9 earthquake shook the region on August 21, killing at least 709 persons and injuring thousands. The earthquake struck in two installments of 10 seconds and 15 seconds each and left cracks in 50,000 buildings, including Raj Bhavan and the old Secretariat Building in Patna, Bihar.

The 1995 Neftegorsk earthquake occurred on 28 May at 1:04 local time on northern Sakhalin Island in the Russian Far East. It was the most destructive earthquake known within the current territory of Russia, with a magnitude of Ms7.1 and maximum Mercalli intensity of IX (Violent) that devastated the oil town of Neftegorsk, where 1,989 of its 3,977 citizens were killed, and another 750 injured.

The 2010 Oaxaca earthquake struck Oaxaca, Mexico on June 30, 2010, with an Mw magnitude of 6.3. Many people in different cities left their beds and ran into the street, as the quake struck at 2:22 am. Helicopters and police vehicles were sent to inspect possible damage in Mexico City, primarily in downtown and central areas, where some buildings were evacuated. In Mexico City, some cases of power outage in Azcapotzalco, Iztapalapa, and Benito Juárez and cracks in buildings were reported. 1 person died in San Andrés Huaxpaltepec, Oaxaca.

The 1967 Mudurnu earthquake or more correctly, the 1967 Mudurnu Valley earthquake occurred at about 18:57 local time on 22 July near Mudurnu, Bolu Province, north-western Turkey. The magnitude 7.4 Mw earthquake was one of a series of major and intermediate quakes that have occurred in modern times along the North Anatolian Fault since 1939.

The 2010 Mindanao earthquakes occurred in the southern Philippines in the Moro Gulf. This was a complex sequence of events including three main events of Mw magnitude 7.3 or greater on the 23rd of July, and two significant aftershocks of magnitude 6.6 on the 24th and 29th. All of these were deep focus earthquakes, at depths from 565 km (351 mi) to 634 km (394 mi). This resulted in minimal, but very widespread shaking at the surface, with a maximum intensity of IV on the PEIS scale; consequently there were no reports of casualties or damage.

The 1997 Harnai earthquake occurred on February 27 at 21:08 UTC near Harnai, Pakistan, and felt throughout much of central Balochistan, with a magnitude estimated at 7.0 on the Mw scale. A 2016 study determined that this was a doublet earthquake, the Mw 6.8 shock that hit 19 seconds later being a continuation of the initial main shock. The largest aftershock was an Ms 6.4 shock that hit 22 minutes after the main shock. The earthquake was caused by the collision between the Indian Plate and the Eurasian Plate.

The 1973 Veracruz earthquake, also known as El Terremoto de Orizaba, occurred at 3:50 a.m. local time on August 28, with the epicenter located in the vicinity of Serdán in the Mexican state of Puebla. It registered 7.1 on the moment magnitude scale and had a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale. The effects were felt in the Mexican states of Veracruz and Puebla in southeast Mexico.

The 1997 Cariaco earthquake occurred on July 9 at 15:24:14 local time with a moment magnitude of 6.9 and a maximum Mercalli intensity of VIII (Severe). With its epicenter near Cariaco, Venezuela, at least 81 people were killed and over 500 were injured. Disruption of power, telephone, and water services was reported. This earthquake was felt in much of northeastern Venezuela and could also be felt in Trinidad and Tobago. This earthquake was on the strike-slip El Pilar Fault.

The 1953 Torud earthquake occurred at the northeastern border of the Great Salt Kavir in Torud, Semnan, Iran on 12 February. The shock had a moment magnitude of 6.6 and had a maximum Mercalli intensity of VIII (Severe). At least 800 people were killed.

<span class="mw-page-title-main">1943 Alahan Panjang earthquakes</span> Earthquakes in Indonesia

The 1943 Alahan Panjang earthquakes occurred on June 8 and June 9 UTC in Sumatra, then under Japanese occupation. This was an earthquake doublet.

The 1974 Lesser Antilles earthquake occurred at 05:50:58 local time on October 8 with a moment magnitude of 6.9 and a maximum Mercalli intensity of VIII (Severe). Four people were injured in what the United States' National Geophysical Data Center called a moderately destructive event.

The 1977 Tonga earthquake took place on 22 June at 12:08:33 UTC some 200 km southwest of Tongatapu, which shocks infecting all islands of the kingdom of Tonga. The earthquake measured 8.0 on the moment magnitude scale and had a maximum intensity of VIII (Severe) on the Mercalli intensity scale.

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 Mercalli intensities were VII and VIII, respectively.

On April 13, 1923 at 15:31 UTC, an earthquake occurred off the northern coast of the Kamchatka Peninsula in the USSR, present-day Russia. The earthquake had a surface-wave magnitude (Ms ) of 6.8–7.3 and an estimated moment magnitude (Mw ) of ~8.2. This event came just two months after a slightly larger earthquake with an epicenter struck south of the April event. Both earthquakes were tsunamigenic although the latter generated wave heights far exceeding that of the one in February. After two foreshocks of "moderate force", the main event caused considerable damage. Most of the 36 casualties were the result of the tsunami inundation rather than the earthquake.