HR: 1330h
AN: S42C-0188    [PDF]
TI: The Energy Budget of Earthquake Rupture: a View From Spontaneous Rupture Modeling and Finite-Source Models
AU: * Mai, P
EM: mai@seismo.ifg.ethz.ch
AF: Institute of Geophysics, ETH Hoenggerberg, Zurich, ZH CH-8093 Switzerland
AU: Guatteri, M
EM: mariagiovanna_guatteri@swissre.com
AF: Swiss Reinsurance America, Armonk, New York, NY 10504 United States
AB: It is a common and frustrating experience of many dynamic modelers to initiate spontaneous rupture calculations that subsequently abort before rupturing to the desired earthquake size [\emph{Nielsen and Olsen}, 2000; \emph{Oglesby and Day}, 2002]. Source parameters in such dynamic source models are strongly correlated, but stress drop is the main factor affecting the distribution of the other dynamic rupture parameters. Additionally, the position of the hypocenter exerts a strong influence on the dynamic properties of the earthquake, and certain hypocenter positions are not plausible as those would not lead to spontaneous rupture propagation. To further investigate this last statement, we analyze the energy budget during earthquake rupture using spontaneous dynamic rupture calculations and finite-source rupture models. \\ In describing the energy budget during earthquake rupture, we follow \emph{Favreau and Archuleta} [2003]. Each point on the fault contributes to the radiated seismic energy $E_{rs} = E_{el} - E_{fr} - E_{rx}$, where $E_{el}$ denotes the elasto-static energy and $E_{fr}$ the fracture energy. In this study we neglect for simplicity the relaxation work $E_{rx}$ spent during the stopping of the earthquake. A rupture can be characterized by locally negative seismic energy density values, but its integral over the fault plane must be positive. The fundamental condition for rupture growth is therefore that the integral of $E_{rs}$ on the rupture area remains always positive during rupture propagation. \\ Based on a simple energy budget calculation, we focus on identifying those target slip/stress distribution in dynamic rupture modeling that for a given hypocenter location fail to rupture spontaneously. Additionally, we study the energy budget of finite-source rupture models by analyzing the integrated seismic energy for the inferred slip maps using also hypocenter positions other than the network location. These results indicate how rupture was promoted for the true hypocenter while randomized hypocenters may not have been able to sustain a large earthquake. Our approach helped us both to speed up the computation of successful spontaneous rupture models, as well as to construct dynamically consistent rupture models for strong motion prediction.
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2003 Fall Meeting