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

ISOLated Asperities Time HypocentreMain 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 u = E a

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

Theory – computer modes full 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 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 ratio in analyzed frequency band (SN) 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 resolvability without 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 components of the same source Krizova, Zahradnik and Kiratzi, BSSA submitted Mw 4.9 (AUTH) near Columbo volcano Aegean Sea ISO ~ 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 record red: 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 -User creates his/her header and footer ISOLA - New Features ______________________________________ University of Patras Seismological Laboratory ______________________________________ ====================================== ======= Moment Tensor Solution ======= ====================================== Hypocenter Solution (UPSL) Origin Time : :25:13.83 Lat: Lon: Depth (km) : 7.5 Mw : 4.1 ====================================== Centroid Solution Centroid Time : (sec) relative to origin time Centroid Lat: Lon: Centroid Depth : 7 ====================================== No of Stations: 5 (DSF-GUR-LTK-EFP-UPR) Freq band (Hz) tapered and Variance Reduction (%): 84 Moment Tensor (Nm): Exponent 10**15 Mrr Mtt Mpp Mrt Mrp Mtp VOL (%) : 0 DC (%) : 81.5 CLVD (%) : 18.5 Best Double Couple: Mo= 1.548e+015 Nm NP1: Strike Dip Rake NP2: Strike Dip Rake ####### ################# ############ ########## ######### ######## ###### P ###### ##### ####- # #---- ######## ########---- ############################--- ###########################-- ####### ##############- ##### T ############# ### ########### ####### Moment Tensor Solution computed using ISOLA University of Patras, Geology Department Seismological Laboratory

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) e e+017 …………. ……….. …… ………

Application – Tohoku, Japan 2011 (Mw 9.0) near-regional stations period 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 seconds a single-source approximation

Application – Van, Turkey 2011 (Mw 7.1) near-regional stations 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 earthquake near-regional stations 6-20 seconds: reveal at least 3 slip episodes Uncertainty = other possible scenarios fitting data equally well 19

Application - L’Aquila 2009 (Mw 6.3) Gallovic and Zahradnik, JGR 2012 ISOLA (green circles) validated through comparison with TSVD slip inversion (color) near stations periods 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 stations periods dependent on Mw (basically above 8 seconds)

Application – local event (Mw 0.2) Benetatos, Malek, Verga J. of Seismology, submitted 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)

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 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