Modeling earthquake ground motion with an earthquake simulation program (EMPSYN) that utilizes empirical Green's functions

Technical Report · Wed Jan 01 04:00:00 EST 1992

DOI:https://doi.org/10.2172/5616334· OSTI ID:5616334

Hutchings, L.

This report outlines a method of using empirical Green's functions in an earthquake simulation program EMPSYN that provides realistic seismograms from potential earthquakes. The theory for using empirical Green's functions is developed, implementation of the theory in EMPSYN is outlined, and an example is presented where EMPSYN is used to synthesize observed records from the 1971 San Fernando earthquake. To provide useful synthetic ground motion data from potential earthquakes, synthetic seismograms should model frequencies from 0.5 to 15.0 Hz, the full wave-train energy distribution, and absolute amplitudes. However, high-frequency arrivals are stochastically dependent upon the inhomogeneous geologic structure and irregular fault rupture. The fault rupture can be modeled, but the stochastic nature of faulting is largely an unknown factor in the earthquake process. The effect of inhomogeneous geology can readily be incorporated into synthetic seismograms by using small earthquakes to obtain empirical Green's functions. Small earthquakes with source corner frequencies higher than the site recording limit f{sub max}, or much higher than the frequency of interest, effectively have impulsive point-fault dislocation sources, and their recordings are used as empirical Green's functions. Since empirical Green's functions are actual recordings at a site, they include the effects on seismic waves from all geologic inhomogeneities and include all recordable frequencies, absolute amplitudes, and all phases. They scale only in amplitude with differences in seismic moment. They can provide nearly the exact integrand to the representation relation. Furthermore, since their source events have spatial extent, they can be summed to simulate fault rupture without loss of information, thereby potentially computing the exact representation relation for an extended source earthquake.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5616334
• Report Number(s): UCRL-ID-105890; ON: DE92010358
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
COMPUTER CODES
COMPUTER PROGRAM DOCUMENTATION
COMPUTERIZED SIMULATION
E CODES
EARTHQUAKES
FUNCTIONS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GREEN FUNCTION
GROUND MOTION
MATHEMATICAL MODELS
MOTION
SEISMIC EVENTS
SIMULATION