Mendez, A.

This article describes the results of a ground motion modeling study of the 1915 Avezzano earthquake. The goal was to test assuinptions regarding the rupture process of this earthquake by attempting to model the damage to historical monuments and populated habitats during the earthquake. The methodology used combines stochastic and deterministic modeling techniques to synthesize strong ground motion, starting from a simple characterization of the earthquake source on an extended fault plane. The stochastic component of the methodology is used to simulate high-frequency ground motion oscillations. The envelopes of these synthetic waveforms, however, are simulated in a deterministic way based on the isochron formulation for the calculation of radiated seismic energy. Synthetic acceleration time histories representative of ground motion experienced at the towns of Avezzano, Celano, Ortucchio, and Sora are then analyzed in terms of the damage to historical buildings at these sites. The article also discusses how the same methodology can be adapted to efficiently evaluate various strong motion parameters such as duration and amplitude of ground shaking, at several hundreds of surface sites and as a function of rupture process. The usefulness of such a technique is illustrated through the inodeling of intensity data from the Avezzano earthquake. One of the most interesting results is that it is possible to distinguish between different rupture scenarios for the 1915 earthquake based on the goodness of fit of theoretical intensities to observed values.

The Irpinia project, as carried out by ISMES under a commission from ENEL, had as objectives the developement of a general methodology to simulate broad-band seismic ground motion at near-source and regional distances, and the application of this methodology to the 1980 Irpinia earthquake. Within this general framework, one goal was the comparison of four previously published models for this earthquake in order to arrive at a plausible description of the source process. The comparative study was cast as an inverse problem: that of inferring the spatial extent and temporal behaviour of the rupture process, from geodetic measurements of surface deformation and near-source recordings of ground velocity. This study was complicated by the fact th the Irpinia earthquake was a complex event, involving at least three distinct rupture episodes in a time span of 40 s. However, this same complexity offers the opportunity of illustrating the use of inversion methodologies to 1) infer the spatial slip distribution on a multiple fault system; 2) address the problem of determining the accuracy of the inferred slip models, and 3) use information describing the static characteristics of an earthquakes as an aid in understanding the kinematics of the rupture. This last point is illustrated for the 40 s subevent through the results of a forward modeling study of high-frequency acceleration waveforms using a rupture model based on the inversion results.