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S eismic wave P ropagation and I maging in C omplex media: a E uropean network

S eismic wave P ropagation and I maging in C omplex media: a E uropean network. IVO OPRSAL Experienced Researcher Host Institution: CUP Prague Place of Origin: Czech Republic Appointment Time: July 2005

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S eismic wave P ropagation and I maging in C omplex media: a E uropean network

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  1. Seismic wave Propagation and Imaging in Complex media: a European network • IVO OPRSAL • Experienced Researcher • Host Institution: CUP Prague • Place of Origin: Czech Republic • Appointment Time: July 2005 • Project: Forward and inverse modelling of finite-extent earthquake source by PEXT and FD method. • Task Groups: Local scale • Cooperation: INGV Rome, GFZ Potsdam, ETH Zurich, AIST Tsukuba

  2. Project ScopeKinematic finite-extent source modellingThe Turkey-Flat strong motion "blind" prediction - internationalexperiment The Turkey Flat strong-motion experiment is the forth of the blind prediction experiments, where the Prague group takes a part:- Turkey Flat (Parkfield) weak motion test (1987)- Ashigara valley (Odawara, 1992)- Hyogo-ke n Nanbu earthquake (aka Kobe EQ) (Yokohama, 1998)- 2004 Parkfield M6 earthquake (USA, 2006), The tests are conducted under ESG(Effects of surface geology working group of IASPEI/IAEE), the 2006 ESG meeting will take place in Grenoble. More about the present Turkey-Flat strong-motion test can be found at the California Geological Survey page www.quake.ca.gov/turkeyflat.htm

  3. “Blind” Test Approach • Conduct high quality field and laboratory tests to characterize the geotechnical properties of the site • Collect high-quality measurements of ground response in sediment basin and bordering rock • Distribute only rock records and request predictions at basin recording sites • Release observed basin recordings of and compare with predictions

  4. R2 V1 V2 R1 D2 D1 D3 Phase I : R1 predictions (required synthetics: R2,V1,V2,D1,D2,D3) Phase II: D3 predictions (required synthetics: R2,V1,V2,D1,D2)

  5. Turkey Flat strong-motion prediction by the finite-extent source modelling Usual approach is to focus on local site effects while the excitation is represented by plane incident waves. We emphasise the source effect. The reason is that: Firstly, the studied stations (R2, V1, V2, D1, D2, D3) are inside or around a very shallow stiff-soil sedimentary valley (local effects can be treated using individual 1D models below each receiver). Secondly, the dimensions of the ruptured area (W x L = 15 x 40 km, M6) are too large to be approximated by a planar wave. Composite-source method using a non-uniform fault slip distribution (Ji, 2005) is applied to all stations.

  6. Turkey Flat situation Turkey Flat San Andreas Fault - projection of ruptured area hypocenter

  7. Turkey Flat strong-motion prediction by the finite-extent source modelling Free parameters of the source model are tuned by fitting the available acceleration time history and spectrum at R1 (reference rock site) Acceleration (m/s^2)

  8. Turkey Flat strong-motion prediction by the finite-extent source modelling ADVANTAGE: Synthetics (0-40Hz) at the studied stations R2, V1, V2, D1, D2, D3 (with individual 1D models) are obtained with the same source model as that used for R1  i.e. realistic description of the incoming wave filed

  9. Turkey Flat strong-motion prediction results

  10. Turkey Flat strong motion Prediction, PHASE II NO MORE WORK NEEDED ! Availability of D3 record did not require any additional change. This is an a posteriori justification of the approach

  11. Outlook I Modelling the data for predicted stations after they are released and benchmarking/comparison to solutions of other modellers.

  12. Outlook II Weakness of discussed approach:ground motion modelling was tested at 2 points only (R1, D3) Hence, general applicability of the source modelling will be tested using accelerograms from more CISN stations distributed around the fault.

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