AN: G32A-14
TI: Rapid Finite-Fault Determination from Geodetic Data
AU: M H Murray
AU: D S Dreger
AU: D S Neuhauser
AU: L S Gee
AU: P Segall
AU: B Romanowicz
EM: mmurray@seismo.berkeley.edu; Geophysics Dept., Stanford Univ., CA
AB:   
    We are developing methods to combine geodetic and seismic 
    information to rapidly estimate finite-fault geometry and 
    rupture propagation of earthquakes to aid in hazard 
    mitigation and emergency response activities. 
    Finite-fault parameters help to predict static surface 
    deformation changes to flood plains or navigational hazards 
    in coastal areas, stress changes on nearby faults that 
    advance or retard the probability of future earthquakes, 
    and strong ground motion maps for rapid damage assessment.
    These methods will augment the Seismographic Station's 
    Rapid Earthquake Data Integration (REDI) project, which 
    currently relies solely on seismic data for earthquake 
    notification, by adding complementary information from 
    coseismic static displacements measured geodetically. 
    The displacements can be used to resolve nodal plane 
    ambiguity and infer the location and extent of the rupture 
    plane before it is well defined by aftershock locations, 
    and to infer distributions of fault slip that are unbiased 
    by rupture velocity and dislocation rise time assumptions. 
    To be useful in emergency situations, the geodetic
    observations must be processed and combined with the
    seismic observations quickly and automatically.
    We use frame relay telemetry at many of the
    Bay Area Regional Deformation (BARD) permanent 
    GPS stations for rapid, robust access to the observations, 
    and are developing near real-time procedures for detecting 
    coseismic offsets in the presence of high-frequency noise 
    sources, such as multipath and loss of phase lock.
    We use non-linear optimization methods, including hybrid 
    Monte Carlo/gradient techniques, to rapidly estimate 
    finite-fault parameters from the coseismic offsets when 
    the fault geometry is not known a priori. 
    And we are investigating several approaches to combine the 
    geodetic and seismic observations, such as predicting 
    ground motion from the finite-fault parameters using 
    point-source summation forward modeling techniques, as well 
    as simultaneously inverting both geodetic and seismic
    observations.
SC: G
DE: 7215
DE: 1209
MN: Fall Meeting 1996