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Source Inversion Validation (SIV): Quantifying Uncertainties in Earthquake Source Inversions. Martin Mai Morgan Page Danijel Schorlemmer. Earthquake rupture models. - PowerPoint PPT Presentation
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SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 1
Source Inversion Validation (SIV):Quantifying Uncertainties in Earthquake Source Inversions
Martin MaiMorgan Page
Danijel Schorlemmer
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 2
Finite-source inversion are done Finite-source inversion are done almost routinely today, using a almost routinely today, using a variety of inversion / modeling variety of inversion / modeling approaches, different data sets approaches, different data sets and processing stepsand processing steps
We use the slip models to infer We use the slip models to infer rupture dynamics, to devise rupture dynamics, to devise source-characterization source-characterization methods for ground-motion methods for ground-motion simulations, to perform simulations, to perform Coulomb stress modeling, to ….Coulomb stress modeling, to ….
But: how “good”, i.e. But: how “good”, i.e. reliable and robust, are reliable and robust, are these rupture models ?these rupture models ?
Earthquake rupture modelsEarthquake rupture models
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 3
In cases where multiple slip-inversion solutions exist for a single earthquake In cases where multiple slip-inversion solutions exist for a single earthquake we often find striking differences in the slip maps!we often find striking differences in the slip maps!
What drives the large differences between these slip models? What drives the large differences between these slip models?
A suite of models for the 1999 Izmit (M 7.5) earthquake
Intra-event variabilityIntra-event variability
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 4
In cases where multiple slip-inversion solutions exist for a single earthquake In cases where multiple slip-inversion solutions exist for a single earthquake we often find striking differences in the slip maps!we often find striking differences in the slip maps!
What drives the large differences between these slip models? What drives the large differences between these slip models?
A suite of preliminary investigations of the large Chile earthquake
Intra-event variabilityIntra-event variability
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 5
Initial Project:SPICE BLIND TEST
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 6
Source geometry and station distribution similar to the 2000 Tottori earthquake Synthetic seismograms for 19 (33) near-fault sites (COMPSYN, fmax ~ 3 Hz) Known: seismic moment: 1.43 x 1019 Nm, geometry (strike, dip, rake: 150°, 90°, 180°),
hypocentral location and depth (Z= 12.5 km), velocity-density structureUnknown: slip on fault plane, rupture velocity & rise time (both constant)
SPICE: Blind Test on Source InversionSPICE: Blind Test on Source Inversion
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 7
9 groups; the slip models from 5 groups are “visually” similar to the input model waveform fits in all cases implied visually a “very good fit” ….
SPICE: Blind Test on Source InversionSPICE: Blind Test on Source Inversion
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 8
Outcome of the blind test was unexpectedOutcome of the blind test was unexpected
Despite the “simplicity” of the input model, inversions could not resolve slip very well; uncertainties in rupture velocity and rise time up to 20%
Despite differences among all inversion solutions, predicted waveforms are remarkably similar (f < 1 Hz), resulting in low misfit values (generally L2-norm)
4 out of 9 inversion results are, statistically speaking, NOT better than a random model with somehow correlated slip!
Issues in the inversion method? Issues in the parameterization? Issues in the provided synthetics (“correct” solution) Issues in the “basics”: Green’s function computation
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 9
Source Inversion Validation
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 10
SPICE source inversion blindtest
March 2005 – Dec 2007; 9 participating groups
Special AGU session (Dec 2007) with invited speakers
Problems: short-lived; no funding; suggested data formats where not used, and
hence lots of manual labor to generate comparisons
SCEC workshop on earthquake source inversion (Sept. 2008)
~50 participants, 6 invited speakers, and ~3 hrs intense discussions
General consensus that SIV (Source Inversion Validation) has to continue
Collection of general ideas on how to setup the problems and how to organize
ourselves … but no formal decisions or “constitution of a core group”
Past Activities within the SIV InitiativePast Activities within the SIV Initiative
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 11
Proposal to SCEC for financial support for 2009 SCEC-SIV workshop
Dedicated webpage launched (March 2009)
Online platform to distribute the inversion problems and all relevant meta-data
General communication & exchange platform for everyone interested in SIV
Mini-workshop during SSA 2009 (April 2009)
~20 participants for general ~2 hrs discussion on future activities
Step 0: Setup of Green’s function test and initial forward-modeling exercise
Workshop during the Annual SCEC meeting (Sept 2009)
Talks on uncertainty assessment, Bayesian modeling, robustness, source dynamics
Discussions on “Expectations from forward-modeling exercise” and “Simple
inversion exercise”
Discussion on implementation (CSEP-like approach ?)
http://siv.usc.edu
Past Activities within the SIV InitiativePast Activities within the SIV Initiative
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 12
Workshop at KAUST, (March 22-24, 2010)
~20 non-KAUST & 10 KAUST-affiliated participants
3 days of talks and discussions on
Green’s function validation
New approaches to (source) inversion and validation
Addressing uncertainties and differences in source models
Using source models in subsequent work
Computational aspects & testing center
Past Activities within the SIV InitiativePast Activities within the SIV Initiative
How to enjoy snorkeling and not to get
sea-sick in unexpectedly rough waters in
the Red Sea
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 13
Saturday, September 11, 2010 (1:30-5:30pm) Session I: Review of SIV Activities and Green's Function Test Results 1:30 – 1:45 Mai, Page, Schorlemmer: SIV Introduction 1:45 – 2:05 Causse, Mai, and all participants: Results from Green's function test 2:05 – 2:35 Shao & Ji : What did the Exercise of SPICE Source Inversion Validation
BlindTest not Tell You? 2:35 – 3:45 Discussion of Green’s function Results3:45 – 4:00 break Session II: Inversion Techniques & Slip Models 4:00 – 4:20 Song: Does earthquake slip follow Gaussian statistics? 4:20 – 4:50 Lavallee, Archuleta, Schmedes: Spectral analysis of slip spatial distributions 4:50 – 5:30 Discussion of previous talks & plans for Sunday breakout groups
Program for this workshopProgram for this workshop
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 14
Program for this workshopProgram for this workshopSunday, September 12, 2010 (8:00am-12:00pm) Session III: Inversion Techniques and Seismic-Network Geometry 8:00 – 8:30 Ellsworth: Source inversion with minimal assumptions8:30 – 9:00 Meng & Ampuero: Optimal network geometries for source inversion 9:00 – 9:45 Discussion of previous talks, setting up the initial inversion test9:45 – 10:00 break Session IV: Break-Out Session and Open Discussion 10:00-10:45 Breakout groups meet
Preliminary breakout groups: Input/Output formats, station geometry, source models, forward model calculations, misfit functions web tools & development
Where are we heading? What needs to be done? Who does what?
10:45-12:00 Summaries from breakout groups, Open Discussion
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 15
Do all groups compute the Green’s function appropriately? The SIV-project thus start with a zero-order test to verify GF-computations:
“point-source” at 10 km depth, parameterized as a 1 x 1 km2 slip patch with
homogeneous slip and boxcar slip-function of duration τr = 0.2 sec
The shear-modulus at the given depth result in: Mw 4.992, M0 = 3.4992 x 1016
Step 0: Green’s Function ValidationStep 0: Green’s Function Validation
Depth[km]
VP
[km/s]VS
[km/s]Density[g/cm3]
0.0 4.8 2.6 2.3-2.0 4.8 2.6 2.3-2.0 5.5 3.1 2.5-4.8 5.5 3.1 2.5-4.8 6.2 3.6 2.7
-18.0 6.2 3.6 2.7-18.0 6.8 3.8 2.8-24.0 6.8 3.8 2.8-24.0 8.0 4.62 3.2-45.0 8.0 4.62 3.2
point-sourcedepth
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 16
Two cases are considered for the Green’s function test purely left-lateral strike-slip rupture on a vertical fault purely thrust-motion on a 40° dipping fault Stations at Y = 1 km parallel to surface projection of fault plane, and two arrays
that are 30° and 60° rotated from the fault-parallel direction
Step 0: Green’s Function ValidationStep 0: Green’s Function Validation
SCEC Annual Meeting 2010, SIV workshop Sept 11+12, 17
Details on Green’s function test in the next talk