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DATA SETS

The National Strong-Motion Program has the following digital data sets available:

• Digitized Strong-Motion Accelerograms of North and Central American Earthquakes 1933-1986 - a collection of 1,477 mostly three-component station recordings from about 500 earthquakes. These data represent all of the available North American and Hawaiian records written by ground-level instruments.

• National Strong-Motion Network (NSMN) Accelerograms - time series data recorded by NSMN stations for selected earthquakes since 1989 (updated 10/12/2004). Data set also includes 20010113 Mw 7.6 El Salvador earthquake.

• General Earthquake Observation System (GEOS) Accelerograms - recordings collected by the NSMP GEOS project for aftershock studies, long-term deployments, and short-term experiments..

Terminology, processing software, data formats, and download instructions:

• Uncorrected vs Corrected data - the term "uncorrected" indicates that a digitized (or digitally recorded) time series has received no processing that involves any hypotheses as to the character or frequency content of the ground motions or recording instruments. An "uncorrected" analog-recorded time series has been corrected only for uneven film transport with time and for transverse motion of the film as it moved longitudinally through the recorder; it has been shifted to have zero mean; and it has been translated from digitization units to units of cm/sec/sec (ordinates) and seconds (abscissas). The "correction" process applies bandpass filters (removing noise contamination) and instrument correction (removing the effects of frequency-dependent instrument response) to a time series. For a more complete discussion of the processing steps for corrected data see DATA PROCESSING].

• The first line of each data file contains an integer in the first column followed by text that indicates what type of data are contained in the file: "1 UNCORRECTED ACCELEROGRAM" (sometimes referred to as Vol 1), "2 CORRECTED ACCELEROGRAM" (Vol 2), "3 CORRECTED VELOCITY" (Vol 3), "4 CORRECTED DISPLACEMENT" (Vol 4), "5 RESPONSE SPECTRA" (Vol 5), or "6 FOURIER AMPLITUDE SPECTRA OF CORRECTED ACCELERATION" (Vol 6).

• Software, named "BAP", that will correct the time series is also available from the NSMP web site.

• SMC data format - a general description of the SMC data format currently used for NSMP time series.

• Download Instructions: Compressed data files from different earthquakes but from the same station have the same names. Download files from different earthquakes to different directories to avoid overwriting. For example, compressed data files for Station 5295 for the Landers and Big Bear earthquakes are both named "5295.zip" and you may inadvertently overwrite a previously downloaded file if you download them both to the same directory.   You will need a program that decompresses and "unzips" the data.  Uncorrected and corrected data files from the same station for an earthquake will typically have the same names (ex: 0111a.smc for trace a, recorder number 0111).  Download uncorrected and corrected data files to different directories.

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This page was last modified on October 12, 2004.