Computer Programs in Seismology

Computer Programs in Seismology

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 3.30 What’s New?

• Platform support

• gsac

• Upgrade to waveform inversion

• Port of rdseed, evalresp

Version 3.30 Platform 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 parameters of 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 – Test USGS 03 2004 SLU 03 2005 UMR 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.

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 Functions by 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

MFT using sgn stack - HRV-CCM

MFT using pre-whitening

Application to SLU BB Network

GSAC> r [ow]RR.sac [ow]TT.sac [ow]ZZ.sac GSAC> xlim o o 300 GSAC> color rainbow GSAC> p

GSAC> whiten freqlimits 0.005 0.01 0.25 1 absolute GSAC> whiten freqlimits 0.005 0.01 0.25 1 absolute GSAC> p

GSAC> lp c 0.2 n 2 GSAC> p

GSAC> echo now comparing the vertical GSAC> xlim o 50 o 180 GSAC> r [ow]ZZ.sac GSAC> p overlay on

GSAC> whiten GSAC> whiten GSAC> p

GSAC> lp GSAC> p

KMA Velocity Sensors

KWJ-SEO (258 km)

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

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 Frequency Ground Motion Studies

The BOOK