New Source Duration Relationships for Mexican Earthquakes: Practical Application to Stochastic Summation Methods

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Pure and Applied Geophysics

New Source Duration Relationships for Mexican Earthquakes: Practical Application to Stochastic Summation Methods JOEL CRUZ,1 CESAR ARREDONDO,1 Abstract—From the gathering of 127 source time functions (STFs) of seismic events in Mexico, relationships have been developed between the seismic moment (M0) and the total source rupture duration (sd), for normal-faulting inslab, interplate and strike-slipe mechanisms. This relationship has been explored by different authors like Furomoto and Nakanishi (J Geophys Res 88:2191–2198, 1983), Tanioka and Ruff (Seismol Res Lett 68:386–400, 1997), Singh et al. (Bull Seismol Soc Ame 90:468–482, 2000), among others; the latter authors present a similar general relationship for Mexico, considering 53 STFs and with information until 1998. In this research, complementary databases have been integrated, and the available functions updated base on recent research works about the SCARDEC method are used (Valle´e et al. in Geophys J Int 184:338–358, 2011; Valle´e and Douet in Phys Earth Planet Interiors 257:149–157, 2016). With the proposed expressions, it is possible to estimate reasonably, the main parameters of interest for algorithms of stochastic summation, such as the corner frequencies or stress drops in order to simulate strong ground motions, commonly used for source-rupture studies, site-amplification analysis, or for earthquake-resistant design. Besides, a new flexible model of stochastic summation is presented, which allows considering several ways to generate more realistic motions, according to the spectral behavior, both for low and for intermediate frequencies, under earthquakes with moderate and high magnitude; this model was compared with results from a two-stage alternative method considering two corner frequencies. Keywords: Source duration, corner frequency, empirical green’s functions, stochastic summation methods, strong ground motions simulation.

1 ERN Evaluacio´n de Riesgos Naturales y Antropoge´nicos S.A. de C.V, Vito Alessio Robles 179, Col. Hda. Gpe. Chimalistac, ´ lvaro Obrego´n, CP 01050 Mexico, Mexico. E-mail: Del. A [email protected] 2 Instituto de Ingenierı´a, UNAM, Coordinacio´n de Ingenierı´a Estructural, Av. Universidad, No. 3000, Del. Coyoaca´n, CP 04510 Mexico, Mexico.

and MIGUEL JAIMES2 1. Introduction

From the seismological point of view, when it is required to know the effects of a seismic event, it is essential to model it in detail considering the characteristics of the source, the rupture process, the path of propagation and the local conditions. On the other hand and from the engineering perspective, it is of great importance to be able to simulate strong ground motions for a site under future seismic events (e.g., given a magnitude and location), to analyze the structural behavior in a practical way and with a minimum of reference parameters, as discussed in this work. In a previous investigation for Mexico Singh et al. (2000) presented, through a general expression, the existing strong relationship betwe