SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland 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 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

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Project Scope Source 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 tests 4. Application. The 5 April 2003 Stromboli paroxysmal eruption

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Method Source inversion in volcano seismology: synthetic tests and applications INVERSION PROCESS Generation of Green Functions (topography) Data processing Source mechanism (time-dependent) Synthetic data to fit the observations INVERSION *

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Method Source inversion in volcano seismology: synthetic tests and applications INVERSION FOR A VOLCANIC SOURCE 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, 1. Source: moment tensor and single force, time dependent, M pq (t)+F p (t) 2. General formulation for displacement: U n (t) = M pq (t) * G np,q (t) + F p (t)*G np (t) 3. Frequency domain formulation U n (w)=m l (w) g nl (w)

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Synthetic tests Source inversion in volcano seismology: synthetic tests and applications Test 1, Kilauea, Hawaii Geometry, earth structure Fit …retrieving focal depth and epicentral location. Test 2, Stromboli Different constraints on time behaviour of source components: Model

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Stromboli, 5 April 2003: overview Source inversion in volcano seismology: synthetic tests and applications Flank eruption interrupts typical Strombolian activity Landslides at Sciara del Fuoco (SDF) generate a tsunami Jan/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

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Stromboli, 5 April 2003: seismic data Source inversion in volcano seismology: synthetic tests and applications High-frequency blast signal VLP precursor signal

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Stromboli, 5 April 2003: inversion (VLP) Source inversion in volcano seismology: synthetic tests and applications 1. Tensile crack M 0 =1.64x10 15 Nm, M W = Shear crack 3. Pure isotropic source (worse fit) Dip-slip thrust mechanism Misfit ~ 0.15 Fits of displacements:

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Stromboli, 5 April 2003: inversion (blast) Source inversion in volcano seismology: synthetic tests and applications Source components Fits of displacements M 0 =0.61x10 15 Nm, M W =3.8 Time (s) Single Force (x10 9 N) Moment Tensor (x10 16 Nm) Displacement (m)

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland Stromboli, 5 April 2003: modeling Source inversion in volcano seismology: synthetic tests and applications 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. a) b) c) , VLP signal d) , Paroxysm

SPICE Research and Training Workshop III, July 22-28, Kinsale, Ireland 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 eruption Modelling 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 m. Related publications: Cesca and Dahm (2006), Computers and Geosciences, submitted. Cesca, Braun, Tessmer and Dahm (2006), Earth and Planetary Science Letters, submitted.