Computer Programs in Seismology

Robert B. HerrmannSaint Louis University

rbh@eas.slu.edu

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