Stochastic procedure for the simulation of synthetic main shock‐aftershock ground motion sequences

Abstract

Summary According to the current seismic codes, structures are designed to resist the first damaging earthquake during their service life. However, after a strong main shock, a structure may still face damaging aftershocks. The main shock‐aftershock sequence may result in major damage and eventually the collapse of a structure. Current studies on seismic hazard mainly focus on the modeling and simulation of main shocks. This paper proposes a 3‐step procedure to generate main shock‐aftershock sequences of pairs of horizontal components of a ground motion at a site of interest. The first step generates ground motions for the main shock using either a source‐based or site‐based model. The second step generates sequences of aftershocks' magnitudes, locations, and times of occurrence using either a fault‐based or seismicity‐based model. The third step simulates pairs of ground motion components using a new empirical model proposed in this paper. We develop prediction equations for the controlling parameters of a ground motion model, where the predictors are the site condition and the aftershock characteristics from the second step. The coefficients in the prediction equations and the correlation between the model parameters (of the 2 horizontal components of 1 record and of several records in 1 sequence) are estimated using a database of aftershock accelerograms. A backward stepwise deletion method is used to simplify the initial candidate prediction equations and avoid overfitting the data. The procedure, based on easily identifiable engineering parameters, is a useful tool to incorporate effects of aftershocks into seismic analysis and design.

Mainshock‐consistent ground motion record selection for aftershock sequences

“…With respect to source‐to‐site distance, they used the distance R value utilized for the MS earthquake for simplicity. For the same purpose, Hu et al employed the so‐called BASS model . A simpler alternative would be to consider only the largest AS of the sequence which according to Bath is on average 1.2 magnitude units smaller than the MS.…”

“…On the other hand, Jeon et al who carried out an IDA for MSs followed by a cloud analysis for ASs, and Jalayer and Ebrahimian, in their proposed Sequential Cloud Analysis, chose to define different pools of ground motion records for mainshocks and aftershocks before they randomly combine them. Hu et al recently proposed a promising method for simulation of synthetic mainshock‐aftershock ground motions, while Han et al and Goda and Salami or Goda only use as‐recorded mainshock‐aftershock pairs for their cloud and back‐to‐back IDA analyses respectively; this way the dependence between mainshock and aftershock ground motion characteristics is explicitly accounted for.…”

Aftershock Ground Motion Record Selection: A Novel Mainshock-Consistent Approach

“…Several such models can potentially be used, such as the generalized Omori's law [21] used in [22] to simulate time series of earthquakes. Another option adopted in [23] could be the so-called BASS model [24]. A simpler alternative would be to consider only the largest AS of the sequence which according to [11] is on average 1.2 magnitude units smaller than the MS. Herein, we generate sequences by means of the triggering component of the space-time Epidemic-Type Aftershock Sequence (ETAS) model [13].…”

Analysis of the Seismic Demand of High‐Performance Buckling‐Restrained Braces under a Strong Earthquake and Its Aftershocks

“…Without loss of generality, a series of continuous same record could be used to simulate the strong aftershocks or repeated earthquakes [31]. Besides, the selection of the ground motions for simulating the aftershocks could also be consulted by Hu et al and Das et al [32,33]. In this paper, three continuous excitations with the same amplitude are used as the ground motion for a single analysis to consider the effect of an earthquake and its aftershocks.…”