Digital Waveform Data for the Illinois Earthquake of 2008 04 18 09 37 00


This is page describes the digital data collected from the local networks for the Mw=5.3 main event.

All data are contained in the gzip'd tar file ftp://ftp.eas.slu.edu/pub/rbh/20080418093700/20080418093700.tgz

This page discusses the files contained in the tar-ball.

1. Get the tar file

Either use anonymous ftp as follows
        ftp ftp.eas.slu.edu
        Username: anonymous
        Password: yourname@yourmail   (your Email address)
or
       Enter  ftp://ftp.eas.slu.edu/pub/rbh/20080418093700/20080418093700.tgz   on your browser
or  use wget as follows
             wget ftp://ftp.eas.slu.edu/pub/rbh/20080418093700/20080418093700.tgz

2. Unpack the tar file

    gunzip 20080418093700.tgz | tar xvf -             (on windows you you may be able to do this with winzip)

This will create a directory named 20080421053830.DATA  which contains raw data, processing scripts and response files.

3. Directory structure

The directory 20080421053830.DATA  has the following directories

RAW.CERIBB
RAW.CMG5TD
RAW.EPISENSOR
RAW.FBA
RAW.SLUBB

a directory or responses
         
          Resp

and the following processing scripts

DOEVTACCCMG
DOEVTACCEPI
DOEVTVELCERIBB
DOEVTVELSLUBB
DOEVTIUBB
DOROTACC
DOROTVEL



The RAW directories contain the original digital waveform data according to sensor and digitizer:
    RAW.CERIBB - Guralp CMG3-ESP broadband with Guralp DM24 digitizer
    RAW.CMG5TD - Guralp CMG5TD accelerometer
    RAW.EPISENSOR - Kinemetrics EpiSensor accelerometer with Quanterra Q330 digitizer
    RAW.FBA - Kinemetrics FBA-3 accelerometer with Quanterra Q380 digitizer
    RAW.SLUBB - Guralp CMG3-ESP or Nanometrics Trillium or Streckheisen STS-2 broadband seismometer with Quanterra Q380/Q680 or Q330 digitizer

The Resp directory has channel specific pole-zero or generic pole zero for all of the data streams.

The followin script convert the raw data to either ground velocity in units of m/s or ground acceleration in units of m/s/s.

Note 1:  The scripts use the trace manipulation program gsac in the same manner as sac/sac2000. 
Note 2: 
The waveforms are in sac binary format in an INTEL byte order.  The scripts use the program saccvt to ensure the correct byte order for the machine that you are using.
Note 3:  The programs gsac and saccvt are part of the  Computer Programs in Seismology 3.30 package. By clicking on the link you can learn how to download this free package of software for earthquake studies.


Run these scripts first!

DOEVTACCCMG - Create the directory Acc if it does not exist. Place the event coordinates in the Sac trace headers. Remove the instrument response to create ground accleeration in units of m/s/s.  This script uses the same generic response for all CMG5-Td accelerographs.  These data are sampled at 50Hz.  The results are placed in the directory Acc.

DOEVTACCEP - Create the directory Acc if it does not exist. Place the event coordinates in the Sac trace headers. Remove the instrument response to create ground accleeration in units of m/s/s.  This script uses the Episensor/Q330 response defined for each data channel. These data at sampled at 100 Hz. These stations are at SIUC, OLIL and USIN. The results are placed in the directory Acc.

DOEVTACCFBA - Create the directory Acc if it does not exist. Place the event coordinates in the Sac trace headers. Remove the instrument response to create ground accleeration in units of m/s/s.  This script uses the FBA-3/Q680 response defined for each data channel. These data at sampled at 80 Hz. This sensor is adjacent to the broadband at MPH. The results are placed in the directory Acc.

DOEVTVELSLUBB - Create the directory Vel is it does not exist. Place the event coordinates in the Sac trace headers. Remove the instrument response using a FREQLIMITS 0.002 0.004 100 200  for stability at low frequencies. The output will be ground velocity  in m/s from 0.004 Hz to a little less than the Nyquist frequency. The script uses the pole-zero response obtained from the dataless seed for the stations. The results are placed in the directory Vel. The sample rate are 20/40/80 and 100 Hz depending on the channel.

DOEVTVELIUBB - Create the directory Vel is it does not exist. Place the event coordinates in the Sac trace headers. Remove the instrument response using a FREQLIMITS 0.002 0.004 100 200  for stability at low frequencies. The output will be ground velocity  in m/s from 0.004 Hz to a little less than the Nyquist frequency. The script uses the pole-zero response obtained from the dataless seed for the stations. The results are placed in the directory Vel. The sample rate is 20 Hz.

DOEVTVELCERIBB - Create the directory Vel is it does not exist. Place the event coordinates in the Sac trace headers. Remove the instrument response using a FREQLIMITS 0.002 0.004 100 200  for stability at low frequencies. The output will be ground velocity  in m/s from 0.004 Hz to a little less than the Nyquist frequency. The script uses the pole-zero response obtained from the dataless seed for the stations. The results are placed in the directory Vel. The sample rate is 100 Hz.

Now Run these two scripts!

DOROTVEL -
Create the directory Vel.Rot.  High pass fitler the traces with a two pole Butterworth filter at 0.002 Hz for stability. Rotate the traces to vertical, radial and transverse components.  Rename the traces to be of the form StaNetLocCom, e.g., SLMNMBHZ

DOROTACC - Create the directory Acc.Rot.  High pass fitler the traces with a two pole Butterworth filter at 0.02 Hz for stability. Rotate the traces to vertical, radial and transverse components.  Rename the traces to be of the form StaNetLocCom, e.g., SLMNMHNZ