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NEW VERSION OF ISOLA SOFTWARE TO INVERT FULL WAVEFORMS INTO SEISMIC SOURCE MODELS

NEW VERSION OF ISOLA SOFTWARE TO INVERT FULL WAVEFORMS INTO SEISMIC SOURCE MODELS. Efthimios Sokos 1) and Jiri Zahradnik 2) 1) University of Patras, Greece 2) Charles University in Prague, Czech Republic. http://seismo.geology.upatras.gr/isola. ISOL ated A sperities. Time.

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NEW VERSION OF ISOLA SOFTWARE TO INVERT FULL WAVEFORMS INTO SEISMIC SOURCE MODELS

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  1. NEW VERSION OF ISOLA SOFTWARE TO INVERT FULL WAVEFORMS INTO SEISMIC SOURCE MODELS Efthimios Sokos 1) and Jiri Zahradnik2) 1) University of Patras, Greece 2) Charles University in Prague, Czech Republic http://seismo.geology.upatras.gr/isola

  2. ISOLated Asperities Time • 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). Hypocentre Main asperity

  3. Theory - formulation u = E a

  4. Theory – waveform match misfit variance reduction correlation condition number (w… sing. values of the design matrix E)

  5. Theory – computer modes full MT a1, a2, …. a6 deviatoric MT a1, a2, …. a5 (and a6=0) DC-constrained MT a1, a2, …. a5 (and det M =0) , delta or triangle moment-rate time function DW method, spatiotemporal grid search Green fct and elementary seismograms multiple point sources (MPS) iterative deconvolution

  6. Previous summary

  7. 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

  8. ISOLA - New Features • 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)

  9. ISOLA - New Features wrong ! Gallovic and Zahradnik, JGR 2011 • Forward simulation • Synthetic tests revealed possible artifacts for bilateral ruptures

  10. 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 !

  11. ISOLA - New Features Variance Reduction (VR) Signal-to-Noise ratio in analyzed frequency band (SN) Source-station configuration, frequency range and crustal model => Condition Number (CN) Solution Quality VR . SN / CN

  12. ISOLA - New Features Zahradnik and Custodio, BSSA 2012 • Uncertainty assessment • 6D error ellipsoid is numerically constructed • Covers effect of the source-station config. and freq. range

  13. ISOLA - New Features • Uncertainty assessment • Semi-automatic determination of strike/dip/rake ranges • Also available for ISO (=VOL) range

  14. ISOLA - New Features Does not need waveforms, thus enabling mapping of expected MT resolvability without any earthquake observation [= seismic network design]. Zahradnik and Custodio, BSSA 2012 Uncertainty assessment

  15. 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

  16. 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 components of the same source 2009 06 26 Mw 4.9 (AUTH) near Columbo volcano Aegean Sea ISO ~ 50% ISO DC Krizova, Zahradnik and Kiratzi, BSSA submitted

  17. ISOLA - New Features • Automated removal of instrumental disturbances often observed on BB records (e.g. due to tilt) • Special GUI based on Zahradnik & Plesinger, BSSA 2005 and 2010 • Corrected records are saved for further use in inversion

  18. ISOLA - New Features • Automated removal of instrumental disturbances often observed on BB records (e.g. due to tilt) blue: distorted raw displacement record red: corrected record • Special GUI based on Zahradnik & Plesinger, BSSA 2005 and 2010 • Corrected records are saved for further use in inversion

  19. 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

  20. 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

  21. ISOLA - New Features ______________________________________ University of Patras Seismological Laboratory ______________________________________ ====================================== ======= Moment Tensor Solution ======= ====================================== Hypocenter Solution (UPSL) Origin Time : 20081023 03:25:13.83 Lat: 38.1438 Lon: 22.5817 Depth (km) : 7.5 Mw : 4.1 ====================================== Centroid Solution Centroid Time : +1.95 (sec) relative to origin time Centroid Lat: 38.1438 Lon: 22.5817 Centroid Depth : 7 ====================================== No of Stations: 5 (DSF-GUR-LTK-EFP-UPR) Freq band (Hz) 0.05-0.08 tapered 0.04-0.05 and 0.08-0.09 Variance Reduction (%): 84 Moment Tensor (Nm): Exponent 10**15 Mrr Mtt Mpp -0.928 1.113 -0.186 Mrt Mrp Mtp -0.963 -0.236 -0.589 VOL (%) : 0 DC (%) : 81.5 CLVD (%) : 18.5 Best Double Couple: Mo= 1.548e+015 Nm NP1: Strike Dip Rake 319 34 -43 NP2: Strike Dip Rake 86 68 -116 ####### ################# ---------############ ---------------########## --------------------######### -----------------------######## ---------- ------------###### ----------- P -------------###### ----------- --------------##### ----------------------------####- #---------------------------#---- ########-------------########---- ############################--- ############################--- ###########################-- ####### ##############- ##### T ############# ### ########### ####### Moment Tensor Solution computed using ISOLA http://seismo.geology.upatras.gr/isola/ University of Patras, Geology Department Seismological Laboratory http://seismo.geology.upatras.gr • Text summary of the inversion -Easy MT reporting via e-mail -User creates his/her header and footer

  22. 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+018 21.9766 38.4862 -4.7 1.68e+017 …………. ……….. …… ………

  23. Application – Tohoku, Japan 2011 (Mw 9.0) near-regional stations period 10-100 seconds testing ISOLA in an ‘extreme’ case

  24. Application – Van, Turkey 2011 (Mw 7.1) regional stations period 100-200 seconds a single-source approximation Zahradnik and Sokos, report to EMSC 7 days after earthquake

  25. 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.

  26. Van earthquake near-regional stations 6-20 seconds: reveal at least 3 slip episodes Uncertainty = other possible scenarios fitting data equally well 17 19 18

  27. Application - L’Aquila 2009 (Mw 6.3) ISOLA (green circles) validated through comparison with TSVD slip inversion (color) near stations periods 3-16 seconds Gallovic and Zahradnik, JGR 2012

  28. Application – Efpalio 2010 sequence, Greece (30 events Mw 2.5 to 5.3) near-regional stations periods dependent on Mw (basically above 8 seconds) Result: Complex system of shallow normal and strike-slip faults complement the previously known gently dipping structures under Corinth Gulf. Sokos et al., Tectonophysics 2012

  29. Application – local event (Mw 0.2) local stations (up to 3km) depth 1 km periods 0.4 – 0.5 s MT inversion possible down to relatively short periods thanks to proximity of the stations (for which the existing structural model is sufficient) Benetatos, Malek, Verga J. of Seismology, submitted

  30. 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

  31. Thank you for your attention !

  32. ISOLA - New Features - Overview • Uncertainty estimation • Strike, dip, rake and ISO ranges • Seismic network MT resolvability • Validation of spatiotemporal scenarios by perturbations • 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

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