Science Center Objects

Waveform data from the GSN and ANSS backbone are transmitted from the station to the USGS National Earthquake Information Center in near-real time, where they are used for rapid earthquake response.  A small number of stations do not have telemetry, and data from those sites are transmitted to the USGS via media such as tapes or CDs.  As part of GSN and backbone operations, waveform data are reviewed during quality control.  GSN and backbone data are available from the IRIS Data Management Center.

The ASL has scanned a small subset of the WWSSN records and a number of these are available at the IRIS Data Management Center through the Searchable Product Depository.

Available Data:

Data available from IRIS - Information on how to access data from the IRIS Data Management Center

Instrument response information

Probability Density Function plots:

GSN Data Examples:

Travel Time Dataset

As part of our routine review of data we collect, we select data windows around a limited number of larger earthquakes. In the past, we have simply verified that the observed arrivals were acceptably close to predicted arrival times. However, beginning in January 1998, we started to record our arrival time picks as part of our routine data review. Although we typically pick just larger teleseisms, we will usually pick whatever arrivals are visible in the time windows we review. Thus, on occasion, we are picking arrivals from local or regional events.

Our arrival time picks are made from either broadband or short period unfiltered data. We make "classic" picks in the sense that we visually review the time series and mark, to the best of our ability, the onsets of phase arrivals.

Our basic arrival time dataset provides only the station name, the channel from which we made the pick, and the arrival time. We then use a catalog of large teleseisms (the Harvard/Lamont CMT catalog) to perform a rudimentary event and phase association of our arrival time picks. Both the raw and "associated" arrival time datasets are available below.

Please note that the data presented here are experimental. We can make no guarantees about the quality or completeness of these data. Our first and foremost concern is proper quality control of the waveforms--the arrival time datasets presented here are just a byproduct of that work. If you have questions or comments on this project please send mail to: dcc@usgs.gov.

Predicted travel time curves

This plot shows only the associated arrivals, with all sources corrected to 0 km depth. The predicted travel time curves are from the IASPEI tables, for a source depth of 0 km. Note that the 'ghosting' visible preceding the P-arrivals could be due to a single uncataloged preshock. (Public domain.)

Midpoints for Source-Receiver Pairs

This map provides a rough estimate of the data coverage. It shows the geometrical midpoints of the earthquake-to-station great circles, for all the arrivals for which we were able to make event associations (regardless of earthquake depth). For example, if we made a pick of SSS and SKS from a single seismogram, there would just be a single red dot on the map at the exact midpoint of the great circle which connects the earthquake and station. (Public domain.)

Although we continue to make travel time picks and provide them to the ISC and the IRIS Data Management Center, the data set extends from 1997-2005 and is available in two different formats:

  1. raw arrival time picks in tabular form: The columns of this file are, respectively, station name, channel name, and year, day, hour, minute, and second of the phase pick.
  2. "associated" arrival time picks in tabular form: The columns of this file are, respectively, station name, channel name, year, day, hour, minute, and second of the phase pick, year, day, hour, minute, second, latitude, longitude, depth (km) of the associated earthquake, and the phase association.

New Mexico Earthquake

New Mexico Earthquake

The January 4, 1998 Magnitude 3.8 earthquake, approximately 3 miles south of Willard, New Mexico. (Public domain.)

On January 4, 1998, the Albuquerque Seismological Laboratory seismic station ANMO recorded an earthquake with a duration magnitude of 3.8. This earthquake occurred southeast of Albuquerque, just south of Willard, New Mexico. This earthquake is only a few miles from the seismic activity which occurred on New Years Eve. The earthquake plotted (in black) above is the largest of the recent earthquakes which occurred in the area. A microearthquake aftershock with a duration magnitude of less than 1.0 occurred in the same vicinity, approximately 200 seconds after the arrival of the P-wave of the main event.

Plotted in blue and offset above the large seismogram, is the largest of the 5 earthquakes of December 31, 1997, recorded at ANMO, of which at least one was locally felt. This earthquake occurred southeast of Albuquerque, approximately 6 miles northeast of Mountainair, New Mexico. Both earthquakes have been plotted at the same scale. Notice how much larger the amplitude and longer the duration of 3.8 earthquake relative to the 3.0 earthquake.

The arrival times of P and S waves are often used to calculate the origin time and location of earthquakes.  A S-P time of 6.4 seconds gives a distance of approximately 32 miles from the seismic station for the Jan 4, 1998 event, when inserted into an equation which solves for distance taking local geology into account. An analysis of the ground motion recorded on the horizontal components at ANMO (not shown) give a line of south-southeast/north-northwest, coupled with reports or signals recorded from other seismic stations, the direction to the earthquake can be calculated. Other signals recorded by the New Mexico Tech Seismic Networkwere used to "triangulate" a more precise location of the earthquakes. The magnitude given is a duration magnitude, calculated by plugging in the time taken for the recorded signal to return to background noise levels into an equation which accounts for local geology. The duration magnitude is similar to Richter magnitude in that it is a logarithmic scale; however, Richter magnitude is based on the amplitude, rather than the duration, of the recorded signal.

You may also wish to view the past 24 hours of seismic recordings from the ANMO station. This plot is updated every ten minutes, and shows primarily the high frequency seismic energy which is visible from nearby earthquakes. Most of the high frequency energy from large, distant, earthquakes is attenuated while the energy travels from the earthquake to the recording station. Thus, the signal from some large earthquakes may appear smaller on this plot than the signal from much smaller, nearby earthquakes.

Texas Earthquake

A magnitude 3.6 earthquake which occurred in West Texas at 10:33:42 on April 15, 1998 (4:33:42 am Mountain Daylight Time). The earthquake is recorded on the third trace from the top, about halfway across the page.

Texas Earthquake

Recording from Wed 04/15/98 13:30 MDT (Wed 04/15/98 19:30 GMT). (Public domain.)

View Real-time data at ANMO station

Utah Earthquake

A magnitude 3.8 earthquake which occurred in southern Utah at 11:00:40 on June 18, 1998 (05:00:40 am Mountain Daylight Time). The earthquake is recorded on the eighth trace from the top, near the left edge of the page.

Utah Earthquake '98

Recording from Thu 06/18/98 09:20 MDT (Thu 06/18/98 15:20 GMT). (Public domain.)

View Real-time data at ANMO station

Small Explosion

A small test explosion on Kirtland Air Force Base (where ANMO station is located) at about 16:38 on May 28, 1998 (10:38 am Mountain Daylight Time). The explosion is recorded on the ninth trace from the top, about halfway across the page. These small test explosions are a routine occurrence on the Air Force base. The recording shows a large oscillation from the blast and then returns to normal almost immediately (unlike an earthquake).

Small explosion (New Mexico)

Recording from Thu 05/28/98 13:30 MDT (Thu 05/28/98 19:30 GMT). (Public domain.)

View Real-time data at ANMO station