Volcano Watch — Earthquake information for the world

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Whenever a large, destructive earthquake occurs anywhere in the world, such as those in Sumatera and El Salvador on January 13, there is an agency within the U.S. Geological Survey responsible for disseminating information about its location and magnitude on a rapid basis 24 hours a day--the National EarthquakeInformation Center (NEIC).

The center is located in Golden, Colorado, and is staffed by eight to ten seismologists who rotate on-call responsibilities on a weekly basis.

Locating earthquakes anywhere in the world is made possible by transmission of over 150 seismic signals in real time from every continent. Some of these signals are relayed via the internet, while others are brought in by satellite, similar to the way television broadcasts of sporting events can be seen in our living rooms.

An alarm is triggered whenever the signal on a preset number of seismic stations exceeds a threshold. Using a combination of the information given by a pager system and viewing seismic traces from the center via laptop computer, the duty seismologist can determine whether a trip into the office is necessary.

In the event of a large or damaging earthquake, a news release is issued and information about the earthquake is passed on to disaster relief agencies and the U.S. State Department. Information about the earthquake is also posted to NEIC's "Near Real Time Earthquake List": http://neic.usgs.gov/neis/bulletin. When a particularly newsworthy earthquake occurs, news crews from all the major television networks may appear at the office. NEIC staff members may also be requested to provide on-camera interviews at the local affiliates' studios for live or tape-delayed broadcasts.

In addition to serving in this rapid response role, the NEIC is a clearinghouse for earthquake data. Nearly 3,000 seismograph stations around the world report earthquake arrival time data to the NEIC for inclusion in their daily, weekly, and monthly bulletins. The Hawaiian Volcano Observatory currently submits data to NEIC on earthquakes with a magnitude of 4.0 and above. These data allow the NEIC to refine existing earthquake locations and find previously undetected earthquakes.

Locations for over 20,000 earthquakes annually are now published in the monthly bulletin. This number has generally increased over the years due to increases in the number of reporting seismograph stations, faster methods of analyzing the data, and better computers. There are still many parts of the world with relatively few seismometers, making precise locations of smaller earthquakes in these regions difficult.

In cooperation with the International Seismological Centre (ISC) in the United Kingdom, the NEIC maintains a global list of seismograph station codes and coordinates so that every reporting station has a unique code and a traceable history.

The historical earthquake database at the NEIC (http://neic.usgs.gov/neis/epic/epic.html) is searchable, making it a valuable resource for scientists, government agencies, insurance companies, and even the trivia buff.

It is important to keep in mind that, as a global reporting agency, the NEIC will not have data on the very small earthquakes that may occur in Hawai'i or other seismically active parts of the United States. Catalogs containing these data are maintained by the local seismic networks, such as that run by the Hawaiian Volcano Observatory. Nevertheless, for the most important of the millions of earthquakes which undoubtedly occur around the world each year, the NEIC should be the first place to look for information.

Volcano Activity Update

Eruptive activity of Kīlauea Volcano continued unabated at the Pu`u `O`o vent during the past week. Active `a`a and pahoehoe flows are descending Pulama pali, and budding and inflating pahoehoe straddles the eastern boundary of Hawai`i Volcanoes National Park adjacent to the Royal Gardens subdivision. Lava is pooling on the coastal flats and advancing slowly seaward, but none is entering the ocean at this time. The closest active flow is 1.3 km (1 mi) away from the sea coast.

No earthquakes were reported felt in Hawai`i during the week ending on February 15.