NEW VERSION OF ISOLA SOFTWARE TO INVERT FULL WAVEFORMS INTO SEISMIC
SOURCE MODELS
Efthimios Sokos 1) and Jiri Zahradnik 2)
1) University of Patras, Greece2) Charles University in Prague, Czech Republic
http://seismo.geology.upatras.gr/isolahttp://seismo.geology.upatras.gr/isola
ISOLated AsperitiesTime
Hypocentre Main asperity
• Input waveforms in SAC, GCF, SEISAN, PITSA
• Calculations in Fortran – GUI in Matlab
• Graphical User Interface in Matlab (incl. GMT, PS, Google Earth, Ascii and other output formats).
Theory - formulation
qipp q
pqi GMtu ,
3
1
3
1
)(
ipqipq MaM
6 6
1, )()()(
j p q j
jijqip
jpqji tEaGMatu
65432
3651
2164
aaaaa
aaaa
aaaa
Mu = E a
Theory – waveform match
dttu
red)(
1var2
misfit
redcorr varcorrelation
i
jiji dtEatu 2))((
22su
usCorr
)(min
)(max
6,...1
6,...1
ii
ii
w
wCN
variance reduction
condition number(w… sing. values of the design matrix E)
Theory – computer modesfull MT
,
deviatoric MT
a1, a2, …. a6
a1, a2, …. a5 (and a6=0)
a1, a2, …. a5 (and det M =0) DC-constrained MT
moment-rate time function delta or triangle
DW method, spatiotemporal grid search
Green fct and elementary seismograms
multiple point sources (MPS) iterative deconvolution
Previous summary
ISOLA status http://seismo.geology.upatras.gr/isola/
• First release 2004• Currently ~ 100 registered users • Routine use Univ. Patras – Greece (reporting to EMSC)• Central and South America seminar on ISOLA use. Costa Rica &
IASPEI, 2011 – 15 participants
Visitor map July – August 2012
• Forward simulation
– Full MT, deviatoric and DC options
– Useful for preparation of synthetic data
– Useful for a posteriori check of inversion (e.g. for station not used in inversion)
ISOLA - New Features
• Forward simulation
– Synthetic tests revealed possible artifacts for bilateral ruptures
ISOLA - New Features
wrong !
Gallovic and Zahradnik, JGR 2011
ISOLA - New Features• Choosing the low-
frequency range for MT inversion by S/N analysis
(high-frequency
limitation is due to epicentral distance)
- each station may
have a different freq. range !
ISOLA - New Features• Solution
Quality
VR . SN / CN
Variance Reduction (VR)
Signal-to-Noise ratioin analyzed frequencyband (SN)
1 2 3 4 5 6 7 8 9
0
10
20
30
40
50
60
Velocity (km/sec)
Dep
th (
km)
Plot of Vp, Vs CLDRmodif1.da
Vp
Vs
Source-station configuration,frequency range and crustal model => Condition Number (CN)
ISOLA - New Features• Uncertainty
assessment
- 6D error ellipsoid is numerically constructed
- Covers effect of the source-station config. and freq. range
Zahradnik and Custodio, BSSA 2012
ISOLA - New Features• Uncertainty
assessment
- Semi-automatic determination of strike/dip/rake ranges
- Also available for ISO (=VOL) range
ISOLA - New Features• Uncertainty
assessment
Zahradnik and Custodio, BSSA 2012
Does not need waveforms, thus enabling mapping of expected MT resolvabilitywithout any earthquake observation [= seismic network design].
ISOLA - New Features• Time-function (for fixed MT)
-calculated by non-negative least squares
- 1 or 2 source option
-each source may have a different MT
ISOLA - New Features• Time-function (for fixed MT)
each source may have a different MT
a special case:different time functions of the DC and ISO componentsof the same source
Krizova, Zahradnikand Kiratzi, BSSA submitted
2009 06 26Mw 4.9 (AUTH)near Columbo volcanoAegean SeaISO ~ 50%
DC
ISO
ISOLA - New Features
•Special GUI based on Zahradnik & Plesinger, BSSA 2005 and 2010
•Corrected records are saved for further use in inversion
• Automated removal of instrumental disturbances often observed on BB records (e.g. due to tilt)
ISOLA - New Features
•Special GUI based on Zahradnik & Plesinger, BSSA 2005 and 2010
•Corrected records are saved for further use in inversion
• Automated removal of instrumental disturbances often observed on BB records (e.g. due to tilt)
blue: distorted raw displacement recordred: corrected record
ISOLA - New Features• Rotate horizontal components
helpful with acceleration data often not recorded in N, E
-visual control
-data saved for further use in inversion
ISOLA - New Features
• Graphic output summary
- Easy display of MT’s on users’ web pages
- Easily converted to various graphic formats,
- Easily adapted to user needs
• Text summary of the inversion
-Easy MT reporting via e-mail
-User creates his/her header and footer
ISOLA - New Features______________________________________
University of Patras Seismological Laboratory______________________________________
============================================= Moment Tensor Solution ============================================= Hypocenter Solution (UPSL)Origin Time : 20081023 03:25:13.83Lat: 38.1438 Lon: 22.5817Depth (km) : 7.5Mw : 4.1 ======================================Centroid Solution Centroid Time : +1.95 (sec) relative to origin timeCentroid Lat: 38.1438 Lon: 22.5817Centroid Depth : 7 ======================================No of Stations: 5 (DSF-GUR-LTK-EFP-UPR)Freq band (Hz)0.05-0.08 tapered 0.04-0.05 and 0.08-0.09Variance Reduction (%): 84
Moment Tensor (Nm): Exponent 10**15 Mrr Mtt Mpp-0.928 1.113 -0.186 Mrt Mrp Mtp-0.963 -0.236 -0.589VOL (%) : 0DC (%) : 81.5CLVD (%) : 18.5 Best Double Couple: Mo= 1.548e+015 NmNP1: Strike Dip Rake 319 34 -43NP2: Strike Dip Rake 86 68 -116 ####### ################# ---------############ ---------------########## --------------------######### -----------------------######## ---------- ------------###### ----------- P -------------###### ----------- --------------##### ----------------------------####- #---------------------------#---- ########-------------########---- ############################--- ############################--- ###########################-- ####### ##############- ##### T ############# ### ########### ####### Moment Tensor Solution computed using ISOLAhttp://seismo.geology.upatras.gr/isola/
University of Patras, Geology DepartmentSeismological Laboratoryhttp://seismo.geology.upatras.gr
ISOLA - New Features • Spatiotemporal
evolution for extended sources
- Graphic output of the moments (circle radii) and rupture times (colors)
- ASCII text output (e.g. for GPS forward modeling)
LON LAT Time Moment (Nm)21.9118 38.4352 -4.6 1.68e+01821.9766 38.4862 -4.7 1.68e+017…………. ……….. …… ………
Application – Tohoku, Japan 2011 (Mw 9.0)
near-regional stations
period 10-100 seconds
testing ISOLA in an ‘extreme’ case
Application – Van, Turkey 2011 (Mw 7.1)
Zahradnik and Sokos,report to EMSC 7 days after earthquake
regional stations
period 100-200 seconds
a single-sourceapproximation
Application – Van, Turkey 2011 (Mw 7.1)
near-regional stations 10-20 seconds
seeking major subevent
The deviatoric inversion produced a very large (> 50%) spurious non-DC component due to the finite-extent source effect.Thus the major subevent had to be found by the DC-constrained inversion.
Van earthquakenear-regional stations
6-20 seconds:reveal at least 3 slip episodes
17 18
Uncertainty = other possible scenarios
fitting dataequally well
19
Application - L’Aquila 2009 (Mw 6.3)
Gallovic and Zahradnik, JGR 2012
ISOLA (green circles)
validated through comparison with
TSVDslip inversion(color)
near stationsperiods 3-16 seconds
Application – Efpalio 2010 sequence, Greece (30 events Mw 2.5 to 5.3)
Sokos et al., Tectonophysics 2012
Result: Complex system of shallow normal and strike-slip faults complement the previously known gently dipping structures under Corinth Gulf.
near-regional stationsperiods dependent on Mw(basically above 8 seconds)
Application – local event (Mw 0.2)
Benetatos, Malek, VergaJ. of Seismology, submitted
local stations (up to 3km)depth 1 kmperiods 0.4 – 0.5 s
MT inversion possible down to relatively short periods
thanks to proximity of the stations(for which the existing structural modelis sufficient)
Conclusion - why to use ISOLA• Compact package (“all in one”): From raw records
up to publication-quality figures• Routine tool for point source inversion (regional to
local distances), research tool for complex finite-extent sources
• Tested on events Mw 0.2 to 9.0• Windows (most user friendly), Linux and MacOs• All source codes provided to users• Continuous e-mail consultations • Continuing software development & Manual and
Web page
Thank you for your attention !
ISOLA - New Features - Overview• Inversion
– Choosing suitable frequency range by S/N analysis – Different frequency range for different stations– Non-negative moment-rate time function retrieval (for fixed MT)– Removal of instrumental disturbances– Forward simulation tool to design synthetic tests
– Spatiotemporal visualization of source complexity – Different crustal models for different source-station paths
• Uncertainty estimation – Strike, dip, rake and ISO ranges– Seismic network MT resolvability– Validation of spatiotemporal scenarios by perturbations
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