Kinematic earthquake source inversion and tsunami runup prediction with regional geophysical data

Abstract

Rapid near‐source earthquake source modeling relying only on strong motion data is limited by instrumental offsets and magnitude saturation, adversely affecting subsequent tsunami prediction. Seismogeodetic displacement and velocity waveforms estimated from an optimal combination of high‐rate GPS and strong motion data overcome these limitations. Supplementing land‐based data with offshore wave measurements by seafloor pressure sensors and GPS‐equipped buoys can further improve the image of the earthquake source and prediction of tsunami extent, inundation, and runup. We present a kinematic source model obtained from a retrospective real‐time analysis of a heterogeneous data set for the 2011 Mw9.0 Tohoku‐Oki, Japan, earthquake. Our model is consistent with conceptual models of subduction zones, exhibiting depth dependent behavior that is quantified through frequency domain analysis of slip rate functions. The stress drop distribution is found to be significantly more correlated with aftershock locations and mechanism types when off‐shore data are included. The kinematic model parameters are then used as initial conditions in a fully nonlinear tsunami propagation analysis. Notably, we include the horizontal advection of steeply sloping bathymetric features. Comparison with post‐event on‐land survey measurements demonstrates that the tsunami's inundation and runup are predicted with considerable accuracy, only limited in scale by the resolution of available topography and bathymetry. We conclude that it is possible to produce credible and rapid, kinematic source models and tsunami predictions within minutes of earthquake onset time for near‐source coastal regions most susceptible to loss of life and damage to critical infrastructure, regardless of earthquake magnitude.

Subduction zone megathrust earthquakes

“…Efforts are under way to synthesize the accumulated data sets (e.g., Kanamori, 2014;Lay, 2015;Ye et al, 2016bYe et al, , 2016cDenolle and Shearer, 2016;Meier et al, 2017;Melgar and Hayes, 2017;Hayes, 2017), and we will not attempt to summarize the multitude of studies. Large shallow coseismic slip occurred in the 2015 Illapel (e.g., Li et al, 2016;Melgar et al, 2016), 2011 Tohoku (e.g., Lay et al, 2011b;Iinuma et al, 2012;Ozawa et al, 2012;Satake et al, 2013;Romano et al, 2014;Bletery et al, 2014;Melgar and Bock, 2015;Lay, 2017), 2010 Maule (e.g., Vigny et al, 2011;Yue et al, 2014b;Yoshimoto et al, 2016;Maksymowicz, et al, 2017), and 2004 Sumatra (e.g., Ammon et al, 2005;Rhie et al, 2007;Fujii and Satake, 2007) events, accompanying slip on the downdip portions of the megathrusts. In other cases, such as the 2014 Iquique, Chile (e.g., Lay et al, 2014;Hayes et al, 2014b), 2012 Nicoya, Costa Rica (e.g., Yue et al, 2013;Liu et al, 2015), 2003 Tokachi-oki, Japan (e.g., Miyazaki and Larson, 2008;Romano et al, 2010), and 2007 Pisco, Peru, ruptures (e.g., Lay et al, 2010a;Sladen et al, 2010), slip was concentrated on the central or deeper portion of the rupture zone, with no shallow coseismic slip.…”

Line‐of‐sight displacement from ALOS‐2 interferometry: Mw 7.8 Gorkha Earthquake and Mw 7.3 aftershock

“…We used the 1-D layered Earth structure and inversion method of Melgar and Bock [2015]. We assume a planar fault derived from the nodal plane of a W-phase moment tensor inversion [USGS, 2015] with a strike of 295°and a dip of 11°.…”

Slip pulse and resonance of the Kathmandu basin during the 2015 Gorkha earthquake, Nepal

“…To retrieve the kinematics of the seismic rupture, we carried out a formal inversion of time-dependent slip on the fault (23,24) and compared the recorded waveforms with forward predictions assuming a propagating slip pulse with varied characteristics. We assumed a planar fault geometry with a strike of 295° and a dip of 11° in accordance with the teleseismic W-phase moment tensor solution from the USGS (6).…”