computer programs in seismology robert b. herrmann saint louis university [email protected] ...
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Computer Programs in Seismology
Robert B. HerrmannSaint Louis University
http://www.eas.slu.edu/
Tutorials:ftp://ftp.eas.slu.edu/pub/rbh/CPS330.TUT
Organization• Introduction to Computer Programs in Seismology
• CPS installation
• Exercises - Part I
– Surface waves - Group velocity
– Surface waves - Phase velocity
• Lunch
• Insight on seismic hazard estimates from synthetics
• Exercises - Part II
– Joint inversion of receiver functions/dispersion
– Working with SEED data sets
– Shallow Exploration
• Summary
History
• 1971-1974 - Surface Wave Analysis
• 1980’s - Synthetic Seismogram• 1996 - New paradigm
– common file formats• 2002 - Source inversion• 2004 - gsac
Version 3.30What’s New?
• Platform support
• gsac• Upgrade to waveform inversion• Port of rdseed, evalresp
Version 3.30Platform Support
• UNIX (Solaris SPARC/PC, OSF)
• LINUX• MacOSX• Windows
– Cygwin (100%)
Computer Programs in Seismology
GSAC• Basic SAC compatibility
for trace manipulation (19500 lines of C and CALPLOT graphics; 1990 FORTRAN sac > 120,000 lines)
• Use MATLAB for other graphics
• UNIX/LINUX/ MacOSX/ Windows (Cygwin 100%)
• Open source
Implication
• Anyone can now do modern seismology, even with PC running windows, often using FREE compilers and support software
• Anyone!!!• Free!!!• Open!!!
Uses of CPS 3.30
• Source parameter determination
• Inter-station Green’s functions• Synthetics• Determination of shallow velocity
structure
gsac
• Mar 2004, start
• April 2004, trace interaction• Dec 2004, released• Jan 2004, updates base on user
suggestion• Sep 2005, gsac refraction/reflection
module
January 2005• Improvements:
– plot, plotpk - low level plot routines changed to let qdp decimation be controlled by screen resolution
– plot, plotpk - low level plot routines changed to reduce number of non-drawing penup moves
– prs (plotrecordsection) - low level plot routines changed to reduce number of non-drawing penup moves
– cut, xlim - now also take GMT 2004 002 01 02 03 445 and CAL 2004 01 02 01 02 03 455 to define the time window
– GNU readline implemented - the user may use the 4 arrow keys to move around the command line and to view history of commands
• New commands – reverse - reverse a time series – correlate - cross-correlate time series – sign - one bit sgn() operator – stack - stack traces in memory – whiten - force flat amplitude spectrum – markt - put up velocity tics at 1, 2, 3, 4, 5, 6, 7 and 8 km/sec (note that
these values are pre-assigned. The user specification is not yet implemented)
– taper - trace taper implemented– fileid
Source parametersof US Earthquakes
• 155 events (15 Du et al, 43 older SLU, remainder new using USNSN/ANSS data
• Autofeed of waveforms for all m > 3.5 in continental US - do not do California
• Manual analysis and documentation (1 hour)
Focal Mechanisms
Classification and Orientation of Maximum Compressive Stress
Shallow S-velocity
• Site characterization of ANSS sites
• Hazard analysis for St. Louis in particular
SLU – TestUSGS 03 2004SLU 03 2005UMR 01 2005
St. Louis Univ., 4-26-04, S-wave timber source, 4.5 Hz horizontal phones, 1.0 ms
samp int., 1.5 m phone int. No filters or AGC used for display below.
West
East
Multiple?
Direct wave?
Surface
wave?
2nd layer refraction
Bedrock reflection
SITE 43 - Saint Louis University
142174
138169
209
241
318
377
432
572
220
220 360360180
180 1200
1200
340340 500
500 1760
1760
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 1,300 1,400 1,500 1,600 1,700 1,800
Shear Wave Velocity (m/sec)
SHEAR WAVE VELOCITY (m/sec)
USGS S-w ave (refl-refr)
USGS P-w ave (refr)
USGS ReMi S-w ave
bedrock r efl ection
Model Comparison
Observations
• Surface waves have a resolution within a restricted depth range
zmin < z < zmax
• Refractions and especially reflections provide strong constraint
Walk away 24 channel Hammer source, 4.5 Hz vertical geophones
Phase velocity analysis using do_pom
Comparison of a surf96 inversion to R. A. Williams Vs from SH refraction/reflection
Forward prediction of Rayleigh wave phase velocity from R. W. Williams Vs model
Insight
• Combine refraction and reflection data with surface wave dispersion to define velocity structure
Current Effort• Complete tutorial
– Field experiment organization and documentation
– Conversion from SEG2– Surface-wave analysis– Refraction/reflection
analysis (gsac) Done!– Joint inversion– Documentation
Challenges
• Use apparent dispersion – follow Japanese papers to select effective mode
• Use H/Z ratio from noise test to improve depth resolution
• Build reflection constraint into inversion or just use Monte Carlo
Empirical Green’s Functionsby cross-correlation of noise
• Campillo and Paul
• Shapiro and Campillo
Cross-correlate continuous ground noise recordings. Result is proportional to medium response of a impulsive point source applied at surface (Wappenaar, 2004)
Original
• 1 day segments
• Convert to 1-bit through sgn()• Cross-correlate• Stack• Analyze using MFT (ftan)
Problems
• In spite of 1-bit, spectral peaks which means that MFT must be tailored and plots
Sgn bit stack
Whitened stack
MFT using sgn stack - HRV-CCM
MFT using pre-whitening
Application to SLU BB Network
28 pairs
Noisy
Rayleigh wave pulse
Only a few have discernible dispersion from MFT, such at BLO-FVM path
GSAC> r [ow]RR.sac [ow]TT.sac [ow]ZZ.sacGSAC> xlim o o 300GSAC> color rainbowGSAC> p
GSAC> whiten freqlimits 0.005 0.01 0.25 1 absoluteGSAC> whiten freqlimits 0.005 0.01 0.25 1 absoluteGSAC> p
GSAC> lp c 0.2 n 2GSAC> p
GSAC> echo now comparing the verticalGSAC> xlim o 50 o 180GSAC> r [ow]ZZ.sacGSAC> p overlay on
GSAC> whitenGSAC> whitenGSAC> p
GSAC> lpGSAC> p
KMA Velocity Sensors
KWJ-SEO (258 km)GSAC> r kwjbhrseobhr.WSTK kwjThebhtseobht.WSTK kwjbhzseobhz.WSTK
GSAC> hp c 0.1 n 2 p 2
GSAC> lp c 1 n 2 p 2
Rayleigh-wave group velocity
Observations• Do not understand circumstances for
success of failure of technique to get dispersion – sensors? path?
• Getting dispersion requires ad hoc filtering
• Perhaps value is to use empirical Green’s functions as test data for 3-D simulations
• Prefer whitened to 1-bit stack
Version 3.35
• Transverse Isotropy (?)
– surface wave modeling– surface wave inversion
• Shallow S-wave velocity determination – SPAC, ESAC (?)– Joint inversion of refraction survey
dispersion and first arrivals
The BOOK
300 pages typeset so far
Computer Programs in Seismology
• 1975 - v 1.0 - documentation of programs for dissertation
• 1980’s - new techniques• 1996 - modern set
– Easier to use, different paradigm– Tutorials (200 pages each)
• 2005 - very good research package
Computer Programs in Seismology 3.30
• Skill
• Open Source• Target
– Students– Researchers
• Platforms– Solaris (SPARC), LINUX, MacOS-X,
Windows (CYGWIN)• Documentation!!! (needs more)
Computer Programs in Seismology
Version 3.30
• UNIX
• LINUX• MacOSX• Windows
– Cygwin (100%) (free)
What is new 3.30
• Modified wvfgrd96 to permit time shifts
• Minor changes in fmplot and other routines
• Integrated location program• Routinely used for source mechanism
studies in US and Korea• and
GSAC• Basic SAC compatibility for
trace manipulation (19500 lines of C +CALPLOT graphics; 1990 FORTRAN sac > 120,000 lines)
• Use MATLAB for other graphics
• UNIX/LINUX/ MacOSX/ Windows (Cygwin 100%)
• Open source
Goal
• Simple code, simple use
• Distributable• Generally compatible with SAC2000• Tool for students
Differences
• Tutorials
• Help indicates abbreviated syntax• Subset of essential commands
implemented• Better
– color, windowing– plot metafile
– Rotate, rotate3
– plotrecordsection or prs– uses externally created evalresp afile
and pfile– suited to shell script– glob (wild cards)– history – readline editing
• Easily GUI’fied• Trivial to extend
CPS 3.30
• Complete integrated package for regional wave modeling
• Useful for initial data processing in the field
• Data inversion requires more experience and Earth constraints
Version 3.35
• Transverse Isotropy
– surface wave modeling– surface wave inversion
• Shallow S-wave velocity determination – SPAC, ESAC– Joint inversion of refraction survey
dispersion and first arrivals
Version 3.40
• ?
High FrequencyGround Motion Studies
Applied in
Southern California
Southern Great Basin
SE Canada
Korea
Italy (4)
Germany
Switzerland
Yunnan, China
Central US
Utah/Yellowstone
Pacific North West
Southern Spain
Erzican, Turkey
Eastern Turkey
Marmara
S.F. Bay Area
N. California
Sicily
The BOOK
300 pages typeset so far