Magnitude 7.3 quake near Nicobar Islands, India Region

Last updated: 2018-03-26 17:50:55 UTC

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The Anza group at the University of California San Diego operates a broadband seismograph network consisting of 17 three component broadband seismograph stations centered near Anza, California (see map).

On Saturday, December 25th, 2004 at 8:21 PM (PST) we recorded a quake (preliminary mb 7.3) located near Nicobar Islands.

If you felt the quake, the USGS would like to know. Please add to the USGS "Did you feel it?" page.

View the most recent map of local events near San Diego or a slightly wider regional view of events recoded by ANZA, or a map of events recoded by ANZA from around the globe.

Initial source parameters for the recent event are shown below. The epicentral distance (distance separating the epicenter and the closest station in the recording network) for Anza is 14553 km (130.78 degrees).

This map shows the mainshock (red star) and any associated aftershocks (orange stars). Anza network stations are yellow triangles.

Event Map

Global mecator event map

Event Parameters

Latitude	Longitude	Origin time (UTC)	Origin time (PDT)	Depth (km)	mb	Author
6.9000	92.9500	12/26/04 04:21:26.000	12/25/04 (360) 8:21 PM	10	7.3	orbassoc

* The location and magnitude determined for this event are preliminary and are subject to change upon further review of seismic data.

The ANZA broadband network is located in the 'shadow zone' with respect to this earthquake and as a result there is an absence of P-wave energy in the associated seismic waveforms (see below). Find out what the 'shadow zone' is and why it is important in seismic studies: SHADOW ZONE.

You may also view a plot showing

Of local interest:

We operate a broadband station on Piñon Flats Observatory. At (no arrival time recorded) station PFO recorded the P wave from this event. Here is a view of that event as picked by our analyst. A red P indicates a P wave arrival, a red S indicates an S wave arrival.

3 component seismometer recordings at Pinon Flats Observatory

View a larger image showing the waveforms recorded at Piñon Flats Observatory.

Visit the IRIS website with additional links to seismic data for this event.

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Learn more about the Anza group (including who works here, other networks, nuclear tests in China/India/Pakistan).
Learn more about the ANZA network (includes more station information, research, etc).

URL: http://eqinfo.ucsd.edu/special_events/2004/361/b/index.php [Last updated: 2018-03-26 17:50:55 UTC]