U.S. Geological Survey       National Strong-Motion Program

Event Name: Alamo, California Earthquake
Event Date: 09/06/2008, 04:00 UTC (09/05/2008, 09:00 PM PDT)
Event Identification: 20080906_0400
Recorder Type: Kinemetrics: Etna, K2; Ref Tek 130
Network Event ID#: nc51207740

Data Organization and Format ||  Download updated 12/31/2008 ||  Tables updated 12/31/2008

Data Organization and Format

The September 06, 2008, 04:00 UTC, Mw 4.0, Alamo, California Earthquake data recorded by the USGS National Strong-Motion Network (NSMN) are available via the NSMP ftp server in the folder (directory) "20080906_0400" (ftp://smftp.wr.usgs.gov/20080906_0400).    The time series provided are available in uncorrected acceleration, corrected acceleration, corrected velocity, corrected displacement, response spectra (relative displacement, relative velocity, pseudo-velocity, and absolute acceleration), and Fourier amplitude spectra of corrected acceleration.  All of the data are in SMC format.  

In a departure from previous file-naming conventions (where for a particular channel the different time series data all had the same filename, and thus required separate directories for each data type), the file names for the data have the following form:

uncorrected acceleration: RRRRc_u.smc
corrected acceleration: RRRRc_a.smc
corrected velocity: RRRRc_v.smc
corrected displacement RRRRc_d.smc
response spectra: RRRRc_r.rs2
Fourier amplitude spectra (f): RRRRc_f.fs1

where 'RRRR' is the four-digit recorder serial number (including leading 0's) for the USGS data, 'c' is the channel number of the recorder ('a' corresponds to channel 1, 'b' to channel 2 , etc), the '_x' is used to identify the data type, and the suffix refers to the data format (rs2 and fs1 are valid SMC format types recognized by the BAP processing program.

The data are stored in two directories: uncorrected (only uncorrected acceleration) and corrected (all of the corrected and processed data, including acceleration, velocity, displacement, response spectra and Fourier amplitude spectra. This convention for organizing the data was implemented to avoid confusion between the directory names (Vol1, Vol2, … Vol6) previously used for some earlier events and the standard conventions for Volume1, Volume2 and Volume 3 processing.

Information on how the data are processed can be found in the section on DATA PROCESSING.  Note that these data were processed using an acausal Butterworth locut filter.


To facilitate downloading the data, the data have been compressed into PC compatible ".zip" format.  The same zip file is located in the "zips" folder in "20080906_0400/" on the NSMP ftp server, "ftp://smftp.wr.usgs.gov/20080906_0400".   Magnitude Mw 4.1 was corrected to Mw 4.0 on 12/31/2008.  Additional data were added on 12/31/2008 for recorders 9073 (station 1843, San Leandro; Fire Station 9), 9C21 (station 1836, San Leandro; Alameda Co FS11) and 1777 (station 1802, Union City; Fire Station 2).

20080906 04:00 UTC Alamo, California Earthquake Downloads in ".zip" format

20080906_0400_uncorr.zip     uncorrected (2.0 MB; uncompresses to 7.8 MB; updated 12/31/2008)
20080906_0400_corr.zip     corrected 13.0 MB; uncompresses to 37.2 MB); updated 12/31/2008)


List of corrected peak ground accelerations and velocities and pseudo-spectral accelerations for available time-series data, (to obtain list as Excel spreadsheet click here ; click cancel button if get pop-up window requesting user name and password).  Select landscape orientation for printing (In Internet Explorer click on "file", click on "print preview", then click on "landscape" orientation). updated 12/31/2008

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This page was posted on December 19, 2008; updated 12/31/2008.