An Introduction to
Earthquake Analysis Tools
(Part 1)
Bill Langin
10/2/02
Outline
1. Useful websites
2. Obtaining Data
 IRIS-PASSCAL
3. Analysis Programs
 SAC
 HypoInverse
 FOCMEC
Some Useful Websites
1. The IRIS-PASSCAL Homepage
 The source for earthquake data and software
 http://www.iris.edu
 Ordering data, obtain analysis software, get station and/or
array information, instrumentation parameters, etc.
2. OFEUS Geophysical Tools Homepage
 http://orfeus.knmi.nl/other.services/software.links.shtml
 Tools for just about any job…
3. USGS software
 http://quake.wr.usgs.gov/research/software/index.html
4. Harvard Seismology – http://www.seismology.harvard.edu/
Obtaining Earthquake Data
Many tools available on IRIS website
- http://www.iris.washington.edu/
Some useful tools:
- BUD – online buffer of real-time data
- Wilber
- Spyder
useful for looking at data
- Farm
- Weed, Xretrieve – UNIX based tools
- Breqfast – e-mail based data request method
IRIS Data Request Demo
The PASSCAL software
- The most important software for earthquake data analyses
- http://www.iris.washington.edu/DOCS/software.htm
- extraction and manipulation of data
- format conversion, simple processing, archiving
- freely downloadable
- UNIX, Linux
However, you will also need additional tools and will end up
writing a lot of your own code to meet your specific needs.
SAC – Seismic Analysis Code
- SAC has been around for ~20 years and has been the “standard”
in earthquake analysis tools
- http://www.llnl.gov/sac/
- Freely available for UNIX, Linux
- Can be used for just about any manipulation and analysis of
seismic data
- Somewhat “user unfriendly”
- SAC manual is pretty good, online help is better
SAC Demo
- reading files (SAC, SEG-Y, ascii)
- filtering data
- picking
- etc.
Earthquake Location
Lots of choices for location programs:
- HypoInverse – standard used by USGS for 20+ years
- HypoEllipse – created to deal with location in regions with
large amount of relief
- LocSAT – used by CTBT community
- HypoDD – uses “double-difference” technique
- SIMUL12ps – simultaneous inversion for location, Vp, Vs
And there are many more…
HypoInverse
- ftp://swave.wr.usgs.gov/pub/outgoing/klein/hyp2000/
- UNIX or Linux
- relatively simple to get “up and running”
- manual is very detailed and pretty good overall
- input files are ascii text, so can be used on data
from any source
Required Inputs for HypoInverse
You really only need 3 files to get started…
- velocity model
- station location file
- P (and S) pick file
- there are a lot more “bells and whistles” that you can play
with to find the optimal location procedure for your data
HypoInverse Demo
FOCMEC –
A tool for computing
earthquake focal mechanisms
- http://www.geol.vt.edu/outreach/vtso/focmec/
- based on first motion polarities
- can also include SV and SH polarity and amplitude information
- grid search to find all possible solutions with specified number of
tolerable errors
Using FOCMEC
- like HypoInverse, you only need a few files to get started
- station location file
- file with station name and polarity
- file with earthquake location and list of stations to be used
FOCMEC Demo