Physics-Based Earthquake Ground Shaking Scenarios in Large Urban Areas

Abstract

With the ongoing progress of computing power made available not only by large supercomputer facilities but also by relatively common workstations and desktops, physics-based source-to-site 3D numerical simulations of seismic ground motion will likely become the leading and most reliable tool to construct ground shaking scenarios from future earthquakes. This paper aims at providing an overview of recent progress on this subject, by taking advantage of the experience gained during a recent research contract between Politecnico di Milano, Italy, and Munich RE, Germany, with the objective to construct ground shaking scenarios from hypothetical earthquakes in large urban areas worldwide. Within this contract, the SPEED computer code was developed, based on a spectral element formulation enhanced by the Discontinuous Galerkin approach to treat non-conforming meshes. After illustrating the SPEED code, different case studies are overviewed, while the construction of shaking scenarios in the Po river Plain, Italy, is considered in more detail. Referring, in fact, to this case study, the comparison with strong motion records allows one to derive some interesting considerations on the pros and on the present limitations of such approach.

Numerical modeling of seismic waves by discontinuous spectral element methods

“…However, synthetic scenarios produce higher PG values for the velocity field in the proximity of the fault rupture. This has already been noted in many recent works, see [85] and references therein, and may have a great impact on seismic hazard estimates, as standard GMPEs cannot account for such effects. Finally, we also report in Figure 16 some snapshots of the peak ground velocity wave field for a target scenario with magnitude M w 6.5.…”

“…However, the empirical tools that are most often used for this purpose neglect the specific tectonic and geological conditions in which the urban area lies, thus producing in many cases significant underestimations of the earthquake ground motion intensity. An overview of applications of physics-based numerical modelling approaches to large urban areas was presented in [85]. Specifically, SPEED has been applied so far to several case studies, including Christchurch and Wellington (New Zealand), Santiago (Chile), Istanbul (Turkey), and several urban areas in Italy.…”

Physics-Based Scenario of the 2007 Chuetsu-Oki Earthquake

“…The SEM has been successfully used (e.g. [30,31,32]) to simulate 3D seismic wave propagation in complex geological media (and topographical surface) at regional scale with increasing resolution. However, despite the efficiency of the numerical tool used in this study, the calibration of huge 3D large-scale seismic scenarios was conducted with the aid of a less cumbersome yet simplified semi-analytical/numerical tool (i.e.…”

The 3D numerical simulation of near-source ground motion during the Marsica earthquake, central Italy, 100 years later

“…Moreover, DGSE methods can handle non-matching grids and different local approximation degrees making such schemes much more flexible than classical SE approaches from the mesh generation point of view (at price of an increased computational complexity). Finally, DGSE methods enjoy a high level of intrinsic parallelism, making such a discretization technique well suited for massively parallel computations [23]. The present version of SPEED includes the possibility to treat seismic wave propagation in linear and non-linear visco-elastic heterogeneous soils, characterized either with frequency proportional quality factor [24], or frequency constant quality factor [25].…”

“…Recently, SPEED was successfully applied for the numerical simulation of near-source ground motion during the 2012 Po plain seismic sequence in Italy [28], for hazard assessment analysis in large urban areas for reinsurance evaluations as described in [23], as well as for city-site interaction problems and for the dynamic response of extended infrastructures [29].…”