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