Semi-Empirical Estimation of Strong Ground Motions During Large Earthquakes

A synthesis method is developed for estimating deterministically strong motions during the mainshock, using the records of small events such as foreshocks and aftershocks which occurred within the area of the mainshock fault. This synthesis formulation is based on the kinematic source model of Haskell type and the similarity law of earthquakes. The parameters for this synthesis are determined to be consistent with the scaling relations between the moments and the fault parameters such as fault length, width and dislocation rise time. If the ratio of the mainshock moment Mo to the small event one Moe is assumed to be N', then the mainshock fault can be divided into N x N elements, each dimension of which is consistent with that of the small event and N events at each element may be superposed with a specific time delay to correct the difference in the rise time between the mainshock and the small event and to keep a constant slip velocity between them. By means of this method, the mainshock velocity motions are synthesized using the small event records obtained by velocity-typestrong-motion-seismographs for 1980 Izu-Hanto-Toho-Oki Earthquake (M=6.7). The resultant synthesized motions show a good agreement with the observed ones in the frequency range lower than 1 Hz. Further, the synthesis formulation is improved to be applicable to the higher frequency motions, especially acceleration motions. This revised synthesis for the higher frequency motions is effective when we use the records from the small event having the fault length Le-=V,-•T(Vr: rupture velocity and T: rise time of mainshock). The synthesized accelerograms by this revised method are in good agreement with the observed ones in the frequency range up to 5 Hz.

[1]  Hiroo Kanamori,et al.  A semi-empirical approach to prediction of long-period ground motions from great earthquakes , 1979, Bulletin of the Seismological Society of America.

[2]  D. Andrews.  A stochastic fault model: 2. Time‐dependent case , 1981 .

[3]  K. Aki.  Scaling Law of Earthquake Source Time-Function , 1972 .

[4]  I. Kawasaki,et al.  SEISMIC WAVES DUE TO A SHEAR FAULT IN A SEMI-INFINITE MEDIUM , 1973 .

[5]  N. A. Haskell.  Elastic displacements in the near-field of a propagating fault , 1969 .

[6]  K. Aki.  Seismic displacements near a fault , 1968 .

[7]  Takashi Miyatake,et al.  Dynamical rupture process on a three‐dimensional fault with non‐uniform frictions and near‐field seismic waves , 1978 .

[8]  John Boatwright.  A dynamic model for far-field acceleration , 1982 .

[9]  Donald V. Helmberger,et al.  Simulation of strong ground motions , 1980 .

[10]  Keiiti Aki,et al.  Fault plane with barriers: A versatile earthquake model , 1977 .

[11]  Robert J. Geller,et al.  Scaling relations for earthquake source parameters and magnitudes , 1976 .

[12]  K. Aki.  Characterization of barriers on an earthquake fault , 1979 .

[13]  Raul Madariaga,et al.  High-frequency radiation from crack (stress drop) models of earthquake faulting , 1977 .

[14]  S. Hartzell.  Earthquake aftershocks as Green's functions , 1978 .

[15]  Stephen H. Hartzell,et al.  STRONG-MOTION MODELING OF THE IMPERIAL VALLEY EARTHQUAKE OF 1979 , 1982 .

[16]  Michel Bouchon,et al.  A dynamic source model for the San Fernando earthquake , 1978, Bulletin of the Seismological Society of America.

[17]  Raul Madariaga,et al.  On the relation between seismic moment and stress drop in the presence of stress and strength heterogeneity , 1979 .

[18]  R. Sato.  LONG-PERIOD SURFACE VELOCITIES AND ACCELERATIONS DUE TO A DISLOCATION SOURCE MODEL IN A MEDIUM WITH SUPERFICIAL MULTI-LAYERS PART II , 1977 .

[19]  M. Bouchon.  Discrete wave number representation of elastic wave fields in three-space dimensions , 1979 .

[20]  C. Tsuboi.  Earthquake Energy, Earthquake Volume, Aftershock Area, and Strength of the Earth's Crust , 1956 .

[21]  D. L. Anderson,et al.  Theoretical Basis of Some Empirical Relations in Seismology by Hiroo Kanamori And , 1975 .

[22]  K. Abe.  Reliable estimation of the seismic moment of large earthquakes. , 1975 .

[23]  N. A. Haskell.  Radiation pattern of surface waves from point sources in a multi-layered medium , 1964 .

[24]  A. McGarr,et al.  Analysis of peak ground motion in terms of a model of inhomogeneous faulting , 1981 .