Rapid kinematic slip inversion with regional geophysical data: towards site-specific tsunami intensity forecasts.

Abstract:

Rapid kinematic slip inversions immediately following earthquake rupture is traditionally limited to teleseismic data and delayed many hours after large events. Regional data such as strong motion is difficult to incorporate quickly into images of the source process because baseline offsets render the long period portion of the recording unreliable. Recently it’s been demonstrated that high rate GPS can potentially produce rapid slip inversions for large events but is limited to very long periods. With an example of the 2011 M9 Tohoku-oki event we will demonstrate that the optimal on-the-fly combination of GPS and strong motion through a seismogeodetic Kalman filter produces reliable, broadband strong motion displacement and velocity waveforms that can be used for kinematic inversion. Through joint inversion of displacement and velocity waveforms we will show that it is possible to obtain a broadband image of the source. Furthermore, we will also show that it is possible to include offshore geophysical observables such as sea surface measurements of tsunami propagation from GPS buoys and ocean bottom pressure sensors into the kinematic inversion. These data better constrain the shallowest part of rupture. We will use the time-dependent deformation of bathymetry predicted from the inversion results as an initial condition for tsunami propagation and inundation modeling. Through a comparison to post-event survey observations we will demonstrate that it is possible to reproduce the inundation pattern along the coastline in great detail and argue that detailed site-specific forecast of tsunami intensity is achievable with current methods and instrumentation.