Challenges in Rapid Ground Motion Estimation for the Prompt Assessment of Global Urban Earthquakes

We discuss the use of ShakeMap for the rapid evaluation of shaking hazards of all significant earthquakes around the globe. This global ShakeMap is used in a new U.S. Geological Survey system referred to as PAGER, for the Prompt Assessment of Global Earthquakes for Response. PAGER is an automated alarm system, currently in prototype operation. This is being further developed to rapidly and accurately assess the severity of damage caused by an earthquake and to provide emergency relief organizations, government agencies, and the media with an estimate of the societal impact from the potential catastrophe. Although the global ShakeMaps used for PAGER are constrained in part by rapidly gathered ground motion and intensity data via the Internet and with rupture dimensions resolved with automated finite fault analyses, they are fundamentally predictive, relying on our best e#orts at rapidly estimating ground motions. Such a task requires adaptation of a number of seismological tools that we discuss herein. These include the estimation of site amplification on a global basis, the automatic inclusion of strong motion data and macroseismic intensities, incorporating rupture finiteness (mainly rupture dimensions) derived from source modeling, and empirically predicting regionally specific ground motion amplitudes with corresponding instrumental intensities. Since the uncertainties the shaking hazard estimates map into uncertainties in our rapid loss estimates, we also discuss e#orts to quantify the ShakeMap uncertainty as a function of spatial location on the map grid.