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Tools for Seismic Network QCor

Other Uses of Computer Programs in Seismology

Robert B. HerrmannSaint Louis University

INGV24/06/08

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Outline

• Teleseismic and Regional processing requirements

• Incorrect Dataless Seed• Using teleseisms for QC• Using local earthquakes for QC• Instrument response history• Update on Computer Programs in

Seismology

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Background - II have been working with Harley Benz of

the USGS NEIC • to develop replacements for – teleseismic body moment tensor

inversion• to implement – regional moment tensor inversion

• to standardize the computation of synthetic seismograms

Waveform inversion requires high quality, calibrated waveforms

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Example of a data problem

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NORTHEASTERN SAKHA, RUSSIAMagnitude 5.9

2008 June 22 23:56:32 UTC

• Has NEIC CMT:– Strike 108–Dip 44–Rake 59–H 10–Mw 5.9

• Examine waveforms for NM (New Madrid) and NE (New England networks)

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Data

GSAC> map global on ray onGSAC> sh map.shGSAC> convert -trim map.eps map.png

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• Compare observed and predicted ground displacements for the moment tensor solution.

• Units are meters• All signals low pass filtered (function

of Mw) to ignore specific source time function

• FLAG anomalous amplitudes

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Comparison of P on Vertical

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Comparison of SV on Radial

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Comparison of SH on Transverse

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• NM Network OK – problems dues to low frequency noise, not calibration

• NE Network has BIG problems – amplitudes differ by 104 and shapes are wrong

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Background - II

• I am the principal investigator for a regional seismic network sponsored by the USGS

• I must– ensure data flow of calibrated signals to

NEIC in real time– archive all waveforms and metadata at

IRIS

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Broadband Instruments

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Accelerometers

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Quality Control

• Laboratory testing before installation• Testing of dataless seed• Evaluation of real data– teleseisms– local earthquakes

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Laboratory testing• Compare broadband to accelerometer

adjacent to each other (3rd floor [2 piano])– test• wiring• dataless• sensors

– compare reduced ground velocity of Z N E channels in 0.5 – 3 Hz band (good S/N for bb and acc channels)

– compare long period bb to bedrock station 200 meters away

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Trillium (40s)EpisensorQ330

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Discovery

• After reducing to ground motion using evalresp to see effect of FIRs

• discovered problems with earlier evalresp and assumption of symmetric FIRs when we used asymmetric – consequence was different arrival times for LH BH and HH channels for the resultant ground motion.

http://www.eas.slu.edu/Earthquake_Center/NM/INSTRUMENT/

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Comparison of STS-2/Q380 to CMG5TD ground velocity 0.25 – 2

Hz for local earthquake

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Dataless seed

• rdseed -f dateless -R -p– (modified rdseed to get more

information)• use evalresp to get amplitude/phase

response. Emulate step acceleration response

• use pole-zero to get amplitude response. Emulated step acceleration response

• Script for easy usehttp://www.eas.slu.edu/Earthquake_Center/NM/OLIL/OLILindex.html

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Why? Check coordinates, orientations, polarities. Ensure that dataless is compatible with rdseed and evalresp

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Other tools

• USGS NEIC–mdget• All metadata for Continuous Wave Buffer is

loaded from dataless SEED.• mdget permits getting

orientation/coordinates/station/description– in xml and kml

• mdget -kml -s MN.......... > mn.kml

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Return to NE network

• Had gain problem from waveform comparison

• Examine– IRIS Noise spectra– dataless at IRIS

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Extremely noisy. Historically this was a good WWSSN site. Why?Examine response!

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rdseed -f NE.dataless -R -p

then

GSAC> fg impulse delta 0.01 npts 16384GSAC> transfer from vel to polezero subtype

SAC_PZs_NE_WES_BHZ__2003.231.00.00.00.0000_99999.9999.24.60.60.99999

GSAC> fftGSAC> bg pltGSAC> pspGSAC> plotnps -F7 -W10 -EPS -K < P001.PLT >

wesbhz.epsGSAC> convert -trim wesbhz.eps wesbhz.png

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• Response looks like 1 Hz seismometer not 30 sec CMG-40T

• Dataless NOT CORRECT

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Earthquake Data

• If one can use waveforms for source inversion, then one can use predicted waveforms to test calibration–Can do this for teleseisms, and for–Regional earthquakes

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20080303141115 - Orfeus

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Observed/Predicted Filtered Accelerations

Observed (red) and predicted (blue) filtered ground velocities 0.05 – 0.20 Hz (Episensor/Q330) using moment tensor for the earthquake. Differences are due to structure and nodal arrivals.

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Review

• Use different techniques to test dataless SEED, e.g., ground motions from various channels, compare to other instruments at same location, compare to synthetics

• For actual operation, rely on real-time displays

• Periodically use large teleseisms to test functioning and timing

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Question

• How does one ensure that independent accelerometers are functioning correctly if there are no local earthquakes to create a high S/N signal?– If very sensitive, e.g., 0.5g max, then one

can see teleseisms (good for gain and timing check)

– or can one initiate a calibration signal?

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Proper network calibration is absolutely of the highest importance.

Performance must be continually reviewed

Determination of earthquake source parameters is one way to accomplish this.

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Tutorials

* Determination of Receiver Functions * Inversion of Surface-Wave Dispersion and Receiver Functions for Structure * Teleseism Synthetics * Surface-Wave Synthetics and Group Velocity Determination * Surface-Wave Synthetics and Phase Velocity Determination * Phase velocity determination using a seismic network and a real data set New SEP 25, 2007! * SEED - Unpacking to SAC, Deconvolving and Rotating * Cross-correlation of Ground Noise - Example for southeastern Spain * Particle motion plots for focal mechanisms * Synthetic seismograms and site * Instrument response - discussing RESP and polezero formats New OCT 19, 2007! * Synthetics for a Spherical Earth New FEB 06, 2008! * Geometrical Spreading for Teleseism P and S NEW FEB 07, 2008 * Simple Programs to read/write SAC files NEW FEB 12, 2008 * Using Synthetics to Evaluate Station Performance NEW MAR 12, 2008 * Use of hudson96 for high-frequency teleseismic P-wave synthetics NEW MAR 26, 2008

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• If interested, I will document the scripts for plotting the dataless response history for the Tutorial page

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Changes in Computer Programs in Seismology

• gsac– ppk pquality– fixed rtr, map, dif, computation of

distance, sort, refr, prs– added p1, p2 for backward compatibility–write append suffix prepend prefix– prs true amplitude

– prototyped make gsac loadable into shell so that gsac commands would be bash commands

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• Updated rdseed evalresp to– rdseed4.7.5.slu to provide extra output– evalresp-3.2.38.slu to handle extra long

FIR's (also to compile cross platform)

• A extensive effort on Earth flattening by comparing modal superposition and wavenumber integration synthetics to free oscillation synthetics (mineos)

• Updated travel time routines that are now identical in all codes

• hudson96 for fast high frequency body wave synthetics

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Next?

• Implement and document a complete processing package for shallow Vs determination

• transverse isotropy for surface-waves (actually derived Wang's dissertation equations)