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About the Earthquake Maps

Recent Earthquakes FAQ

The Recent Earthquake information system was developed through a long process that included input from seismologists, graphic artists, and users. Our goal is to provide users with as much information as possible in a timely fashion. Because the number of users continues to grow, we have been forced to make some design choices to maximize the number of users getting information over the web, especially after felt earthquakes. We consider this system a major step forward for the following reasons:

  • It currently combines data from Advanced National Seismic System (ANSS) seismograph networks from around the country.
  • It is mirrored on multiple sites for robust service during earthquake sequences and network problems.
  • It offers complete coverage with no gaps because of an overlapping system of maps.
  • It provides text information on each earthquake and auxiliary information on some of them.

To meet our goal, we had to make many decisions and compromises. We realize that not everyone will agree with our decisions but we do hope that you will read this file and consider why we made them. If you have comments or suggestions please send them to Web_Team. We look forward to hearing from you and hope you will find the Recent Earthquake system useful.

How do I find what I want?

NOTE: Our information changes with time. Sometimes when you look at a page your browser will show you an old copy that it has cached. Check the time on the page and in the map. If it was produced over an hour ago, or if you think something has happened since it was produced, then use the reload feature of your browser to get a new version of the file.

To navigate through these maps you should start at the USA map.

Once you have looked at the USA map click on an area to zoom in. Or you can select the list of earthquakes below the map.

If you click on the USA map and zoom in you can get more information on any earthquake by either clicking on its map symbol or by clicking on its summary information presented in the list of earthquakes. Or, to move to an adjacent map you can click on one of the blue arrows near the edges of the map.

If you click on an earthquake (either on a map or in a list), you will get a page of detailed information. The types of information and where they are located under the tabs is described below.

At any time you can use your back button to return to a previous page, but always remember the note above about reloading if a page seems old.

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What information is available for each earthquake, and where is it under the various tabs?

There are five (5) potential tabs with earthquake information for each event. If there is no information associated with one of the tabs, that tab will not appear on the event page. The tabs and potential information under each is described below. Most earthquakes will have a small subset of this information available. The more significant the earthquake, the more information that will probably be available.

Earthquake Details

  • Msg
  • FE Region
  • Distances from Cities
  • Source
  • Time Zone Information
  • Other Detail Info

Earthquake Summary

  • Small Location Map
  • Tectonic Summary
  • USGS News Release
  • Felt Reports
  • State Information
  • Earthquake Summary Poster
  • Tsunami Info Links
  • Landslides Info Links
  • Volcano Info Links
  • Photos
  • FAQs
  • Other Summary Info

Earthquake Maps

  • Smallest Resolution Map from Latest Earthquakes maps
  • Location Maps
  • ShakeMap
  • Did You Feel It? Map
  • Seismic Hazard Map
  • Earthquake Density Map
  • Topo Map - currently part of NEIC Links
  • Google Map
  • Other Maps

Scientific & Technical Information

  • Focal Mechanism
  • Moment Tensor
  • Historic Moment Tensor
  • Phase Data
  • Seismic Cross Section
  • Seismic Record Section
  • Seismic Hazard Map
  • Travel Times
  • Waveforms
  • Energy & Broadband Solution
  • Other Scitech Links

Additional Information

  • Organization Links
  • News Links
  • Other Resources Links

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What pages should I bookmark?

You may want to bookmark the USA map as well as more detailed maps for the area where you live and work and others that you find interesting. This may help you get fast access after significant earthquakes when many people are trying to use the Recent Earthquakes system.

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Why are squares used for the earthquakes?

Some users prefer to see earthquakes drawn as circles. We have chosen to use squares because computer screens are based on a square grid of dots or rasters. This makes it easier to draw a clear square than a circle. To draw a good looking circle requires a technique called anti-aliasing, however this introduces shades of grey into the image which makes the map files larger and slower to transfer.

We agree that circles are prettier than squares, and we anticipate that as software and hardware get better and faster, it will be more feasible to use circles. Right now we have opted for the simplicity and visual clarity of squares.

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How were the symbol sizes chosen?

Some users have noted that the magnitude 1, 2, and 3 earthquakes are drawn with fairly small symbols. This was done because after a large earthquake there will be many small aftershocks. If the aftershocks have large symbols they may obscure the mainshock on the map. To help prevent this we have made the small earthquakes have small symbols.

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How were the colors chosen?

Our goal was to highlight the earthquakes while also showing background information such as faults, roads, towns, and bodies of water. We limited our color choices by selecting from the approximately 200 "browser safe" colors that are consistently displayed without dithering by a variety of web browsers. We also attempted to select colors that could be easily distinguished by users with red-green color blindness.

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Why don't the maps show topography?

Some of our older earthquake maps showed topography in the background as either a range of colors or shades of gray. Unfortunately, this popular feature makes the map files about three times larger. These larger files take longer to transfer and at times of heavy usage can prevent us from serving many of those who want the earthquake information. While we would like to show the topography, we have concluded that it is more important to provide fast access to the earthquake data to as many people as possible.

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What do "last hour", "last day" and "last week" mean?

Each map shows the time it was created. The phrases "last hour", "last day", and "last week" are with respect to that time. Any earthquakes that occurred within one hour of the creation time are in the "last hour" and are colored red. Those that occurred between 1 and 24 hours before the map was created are in the "last day" and are colored orange (for the World maps, blue for the US maps). Those that occurred between 24 hours and 7 days (168 hours) before the map was drawn are in the "last week" and are colored yellow.

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How do the earthquakes get here?

Another page describes how the earthquake information gets onto the web server.

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Why do some earthquakes disappear?

The earthquake data shown here is automatically generated and despite our best efforts some glitches will create bogus earthquakes. When we find a bogus event, usually by studying the seismograms, we delete it and careful observers may notice that an earthquake has disappeared. This often happens after a large earthquake when our systems don't realize that all of the seismograms were created by a single event. In this case, one earthquake will turn into multiple "events" on the maps. In other cases problems in our telemetry systems that bring the data from our seismometers to our computers create glitches that also can create bogus events. For these reasons it is very important to remember that this data is preliminary and when events disappear they weren't real to begin with.

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Why isn't the distance to the nearest fault provided?

Seismologists evaluate the hypocenter location and the focal mechanism of an earthquake to decide if the earthquake occurs on a named fault. Research shows that many earthquakes occur on small, un-named faults located near well known faults. For example, most of the aftershocks of the 1989 M6.9 Loma Prieta earthquake occurred on small, subsidiary faults within a few hundred meters of the mainshock rupture plane. On other fault segments like the San Andreas fault near Parkfield, most of the earthquakes occur on the San Andreas fault. It is difficult to automate this decision process, and it would be misleading to imply on the basis of only distance that an earthquake occurs on a named fault.

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How did you decide which places to use for computing the distance to individual earthquakes?

The list of "populated places" comes from the U.S. Census Bureau Census 2000 gazetteer of places. We sort the list based on population, then choose the four places closest to epicenter. We check to see that at least one of the names is shown on the map, or that one place on the list has a population of at least 100,000 people.

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What is the reference point for the places?

The reference point for the descriptive locations is either the City Hall of the town (or prominent intersection in the middle of town if there is no City Hall).

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How did you decide which places to plot on the maps?

The list of places comes from the U.S. Census Bureau Census 2000 gazetteer of places. The name-selection scheme places priority on population while requiring locations to be separated by a minimum specified distance. The algorithm attempts to find at least 4 names on a map, with one in each quadrant of the map. It begins with a requirement for a minimum population (16,000/64,000, respectively, for the 2/10 deg maps) and a minimum location separation of 25/130 km, respectively, within each map. For those maps in which the algorithm could not find one populated place above the minimum population within each quadrant of the map, it progressively relaxed the population criteria to a minimum of 100/25,000, respectively, or until it found a place in the quadrant. In Alaska where the population is sparse, any place was accepted if it didn't violate the separation rule. Almost all places with a population greater than 350,000 are guaranteed a place on the map.

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Recent Earthquakes Data Sources & Contributing Networks

US, International, and offshore regions:

Alaska:

Central and Southeastern US data:

Hawaiian data:

Nevada data:

Northeast data:

Northern California data:

Pacific Northwest data:

Puerto Rico data:

Southern California data:

Utah and Yellowstone data:

All members of the ...

Map Information and Data Sources

Map Software, Coastlines, State and International Boundaries

Populated Places:

Faults

  • Preliminary data from Quaternary Fault and Fold Database for the United States (web page under construction at the USGS Geologic Hazards Program).

Highways and Roads

Contacts

National Earthquake Information Center (NEIC)

U.S. Geological Survey
National Earthquake Information Center
Box 25046, DFC, MS 967
Denver, Colorado 80225

Earthquake Information Line: 303-273-8516
(Recorded information on earthquakes occurring during the previous 24 hours.)
Operations: 303-273-8500
Fax: 303-273-8450
Web Page: http://earthquake.usgs.gov/regional/neic/
E-mail: sedas@neis.cr.usgs.gov

Alaska Earthquake Information Center (AEIC)

Alaska Earthquake Information Center (AEIC)
Geophysical Institute
University of Alaska Fairbanks
903 Koyukuk Drive
Fairbanks, AK 99775-7320

Voice: 907-474-7320
Fax: 907-474-7125
Web Page: http://www.aeic.alaska.edu/
E-mail: webmaster@giseis.akaska.edu

West Coast and Alaska Tsunami Warning Center/NOAA/NWS

West Coast and Alaska Tsunami Warning Center/NOAA/NWS
910 S. Felton St.
Palmer, AK 99645

Web Page: http://wcatwc.arh.noaa.gov/
E-mail: wcatwc@wcatwc.gov

Cooperative New Madrid Seismic Network

Center for Earthquake Research and Information
Campus Box 526590
The University of Memphis
Memphis, TN 38152

Voice: 901-678-2007
Fax: 901-678-4734
Web Page: http://folkworm.ceri.memphis.edu/
E-mail: withers@ceri.memphis.edu

Inter-Mountain West Seismic Networks

Earthquake Studies Office
Montana Bureau of Mines and Geology
1300 West Park Street
Butte, MT 59701-8997

Voice: 406-496-4332
Fax: 406-496-4451
Web Page: http://mbmgquake.mtech.edu/
E-mail: mstickney@mtech.edu

Nevada Seismological Laboratory
University of Nevada, Reno
Reno, Nevada

Voice: 775-784-4975
Fax: 775-784-4165
Web Page: http://www.seismo.unr.edu/

University of Utah Seismograph Stations
135 South 1460 East
Salt Lake City, Utah 84112-0111

Voice: 801-581-6274
Fax: 801-585-5585
Web Page: http://www.seis.utah.edu/
E-mail: webmaster@seis.utah.edu

Hawaiian Volcano Observatory Network

U.S. Geological Survey
Hawaiian Volcano Observatory
P O Box 51
Hawaii National Park, Hawaii 96718

Voice: 808-967-7328
Fax: 808-967-8890
Web Page: http://hvo.wr.usgs.gov/
Web Page: http://elsei.wr.usgs.gov/results/seismic/recenteqs/
E-mail: hvowebmaster@hvo.wr.usgs.gov

Northeast

Lamont-Doherty Cooperative Seismographic Network (LCSN)
Lamont-Doherty Earth Observatory of Columbia University
Palisades, NY 10964

Voice: 845-365-8365
Fax: 845-365-8150
Web Page: http://www.ldeo.columbia.edu/LCSN/
E-mail: jha@ldeo.columbia.edu

Weston Observatory
Department of Geology and Geophysics, Boston College
381 Concord Road Weston, MA 02493-1340

Voice: 617-552-8300
Fax: 617-552-8388
Web Page: http://www.bc.edu/bc_org/avp/cas/wesobs/
E-mail: weston.observatory@bc.edu

Massachusetts Institute of Technology (MIT)

Web Page: http://eaps.mit.edu/erl/

Northern California Seismic Network

U.S. Geological Survey
Seismology Section
345 Middlefield Road - MS 977
Menlo Park, CA 94025

Earthquake Info: 650-329-4025
Voice: 650-329-4085
Fax: 650-329-5163
Web Page: http://quake.wr.usgs.gov/
E-mail: ncsn@andreas.wr.usgs.gov

U.C. Berkeley Seismological Laboratory
207 McCone Hall
U.C. Berkeley
Berkeley, CA 94720-4760

Earthquake Info: 510-642-2160
Voice: 510-642-3977
Fax: 510-643-5811
Web Page: http://www.seismo.berkeley.edu/
E-mail: www@seismo.berkeley.edu

Pacific Northwest Seismic Network

Univ. of Washington, Dept. of Earth and Space Sciences
Box 351310
Seattle, WA 98195-1310

Earthquake Info: 206-543-7010
Voice: 206-685-8180 (lab) or 206-543-1190 (department)
Fax: 206-543-0489
Web Page: http://www.ess.washington.edu/SEIS/PNSN/welcome.html
E-mail: seis_web@ess.washington.edu

Puerto Rico Seismic Network

Puerto Rico Seismic Network
Department of Geology
University of Puerto Rico at Mayagüez
PO Box 9017
Mayagüez, PR 00681-9017

Voice: 787-833-8433
Fax: 787-265-1684
Web Page: http://redsismica.uprm.edu/english/
E-mail: staff@redsismica.uprm.edu

Southern California Seismic Network

Southern California Seismic Network
U.S. Geological Survey - Caltech Seismological Laboratory
Pasadena, California

EQ Info: 626/395-6977
Voice: 626/583-7823 or 626/395-6919
Fax: 626/583-7827
Web Page: http://earthquake.usgs.gov/regional/sca/
Web Page: http://www.seismolab.caltech.edu/
Email: lisa@usgs.gov