A 98-Station Seismic Array to Record Aftershocks of the 1994 Northridge Earthquake


This report is intended to document the NEAR (Northridge Earthquake Aftershock Recording) experiment and data set so that it can be used by others in the seismological community.

During March 26 to April 16, 1994 an array of 98 digital (Reftek) seismic stations recorded over 1,000 Northridge aftershocks. Fifty-three aftershocks were recorded by 40 or more stations.

The stations were located in two clusters in Sherman Oaks and Santa Monica, respectively, and along two profiles traversing the San Fernando Valley and the NW part of the Los Angeles Basin.

A triggering mode with 125 samples per second, 20~s pre-triggering length, and 60~s post- triggering length was used. The data set has been sorted into event files and submitted to both the SCEC (Southern California Earthquake Center) and IRIS (Incorporated Research Institutions for Seismology) data centers. Seventy-five stations were equipped with L28 4.5 Hz sensors, eight with L22 2.0 Hz sensors and fifteen with L4C 1 Hz sensors. All stations were equipped with 3-component seismometers. Among the over 200,000 files recorded by the network, 37,107 files were sorted into 1550 events. The total size of the sorted waveform data is 1.3 Gigabytes.

The data is in SEGY format, which can be easily converted into SAC, AH, SEED, and SIERRA format using codes provided by the IRIS data center.


Geosciences and Geological and Petroleum Engineering

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Technical Report

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© 1996 Geological Survey (U.S.), All rights reserved.

Publication Date

01 Jan 1996