1 / 12

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. SIMONE CESCA Experienced Researcher Host Institution: University of Hamburg Place of Origin: Milano, Italy Appointment Time: July 2005

teva
Download Presentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Seismic wave Propagation and Imaging in Complex media: a European network • SIMONE CESCA • Experienced Researcher • Host Institution: University of Hamburg • Place of Origin: Milano, Italy • Appointment Time: July 2005 • Project: Source inversion in volcano seismology: synthetic tests and applications. • Task Groups: TG Small Scale • Cooperation: INGV Oss. Sismologico Arezzo, Univ. College Dublin, CNRS Clermont-Ferrand

  2. Project ScopeSource inversion in volcano seismology: synthetic tests and applications 1. Generation of GF including topography (Tessmer et al., 2003)2. Frequency domain inversion code to retrieve time-dependent volcanic sources 3. Synthetic tests4. Application. The 5 April 2003 Stromboli paroxysmal eruption

  3. MethodSource inversion in volcano seismology: synthetic tests and applications Generation of Green Functions (topography) Data processing INVERSION PROCESS INVERSION * Synthetic data to fit the observations Source mechanism (time-dependent)

  4. MethodSource inversion in volcano seismology: synthetic tests and applications INVERSION FOR A VOLCANIC SOURCE • 1. Source: moment tensor and single force, time dependent, Mpq(t)+Fp(t) • 2. General formulation for displacement: • Un(t) = Mpq(t) * Gnp,q(t) + Fp(t)*Gnp(t) • 3. Frequency domain formulation • Un(w)=ml(w) gnl(w) 4. Inversion process (matrix form, for each frequency value): U [Ntr.x1] = G [Ntr.x9] M [9x1] 5. Constraints on the time-behaviour of source components: by singular value decomposition VOLPIS Code, http://www.spice-rtn.org

  5. Synthetic testsSource inversion in volcano seismology: synthetic tests and applications Test 1, Kilauea, Hawaii Test 2, Stromboli Model Geometry, earth structure Fit Different constraints on time behaviour of source components: …retrieving focal depth and epicentral location.

  6. Stromboli, 5 April 2003: overview Source inversion in volcano seismology: synthetic tests and applications 28.12.2002 Flank eruption interrupts typical Strombolian activity30.12.2002 Landslides at Sciara del Fuoco (SDF) generate a tsunamiJan/Feb 2003 Effusive activity at SDF (fissure 500m)Feb/Apr 2003 Effusive activity at SDF (fissure 670m)5 April 2003 Paroxysmal explosion from the upper craters: first emission of gas and ash, followed by a large blast and pyroclastic flow Modeling of source mechanism and eruption dynamic by the inversion of broadband seismic data

  7. Stromboli, 5 April 2003: seismic data Source inversion in volcano seismology: synthetic tests and applications VLP precursor signal High-frequency blast signal

  8. Stromboli, 5 April 2003: inversion (VLP) Source inversion in volcano seismology: synthetic tests and applications 1. Tensile crack Dip-slip thrust mechanism Misfit ~ 0.15 Fits of displacements: 2. Shear crack M0=1.64x1015Nm, MW=4.0 3. Pure isotropic source (worse fit)

  9. Stromboli, 5 April 2003: inversion (blast) Source inversion in volcano seismology: synthetic tests and applications Source components Fits of displacements Moment Tensor (x1016 Nm) Displacement (m) Single Force (x109 N) Time (s) Time (s) M0=0.61x1015Nm, MW=3.8

  10. Stromboli, 5 April 2003: modelingSource inversion in volcano seismology: synthetic tests and applications a) 30.12.02-15.2.03 c) 5.4.03, VLP signal b) 15.2-1.4.03 d) 5.4.03, Paroxysm NW-SE cross section of Stromboli topography. Geometry of the focal mechanism responsible for the VLP signal, showing station location and a sketch of the upper conduit.

  11. Conclusions VOLPIS Code for the inversion of volcanic events Synthetic tests proving stability of the inversion, retrieval of time-dependent source components, additional information on source depth and location Application to the 5 April 2003 Stromboli paroxysmal eruptionModelling of the whole eruptive process: as a consequence of the increased pressure of the dike, a slow dip-slip thrust mechamism occurs along the preferential plane of a pre-existing fracture. This mechanism mechanically triggers the opening of the upper conduit and the paroxysm. Estimations of the slip at the fault give values in the range 0.2-0.8m.Related publications:Cesca and Dahm (2006), Computers and Geosciences, submitted.Cesca, Braun, Tessmer and Dahm (2006), Earth and Planetary Science Letters, submitted.

More Related