Simulations of strong ground motion for earthquakes in the Mexicali--Imperial Valley region

Abstract

In this paper computer modelling is used t o test simple approximations for simulating strong ground motions for moderate and large earthquakes in the Mexicali-Imperial Valley region. Initially, we represent an earthquake rupture process as a series of many independent small earthquakes distributed in a somewhat random manner in both space and time along the rupture surface. By summing real seismograms for small earthquakes (used as empirical Green's functions), strong ground motions at specific sites near a fault are calculated. Alternatively, theoretical Green's functions that include frequencies up to 20 Hz are used in essentially similar simulations. The model uses random numbers to emulate some of the non-deterministic irregularities associated with real earthquakes, due either t o complexities in the rupture process itself and/or strong variations in the material properties o f the medium. Simulations of the 1980 June 9 Victoria, Baja California earthquake ( M L = 6.1) approximately agree with the duration of shaking, the maximum ground acceleration, and the frequency content of strong ground motion records obtained a t distances of u p t o 35 km for this moderate earthquake. In the initial stages of modelling we do not introduce any scaling of spectral shape with magnitude, in order to see at what stage the data require it. Surprisingly, such scaling is not critical in going from M = 4-5 events t o the M = 6.1 Victoria earthquake. However, it is clearly required by the El Centro accelerogram for the Imperial Valley 1940 earthquake, which had a much higher moment (Ms -7). We derive the spectral modification function for this event. The resulting model for this magnitude -7 earthquake is then used t o predict the ground motions at short distances from the fault. Predicted peak horizontal accelerations for the M -7 event are about 25-50 per cent higher than those observed for the M = 6.1 Victoria event.

Report of the workshop on Extreme Ground Motions at Yucca Mountain, August 23-25, 2004

“…Munguia and Brune, 1984) found kb stress drop sub-events in the 1980 Victoria, Mexico earthquake (M 6.1). Mori and Shimazaki (1984) interpreted strong motion records of the 1968 Tokachi-oki M 7.9 earthquake as indicating several very high stress-drop subevents (~ 4kb).…”

Simulation of the records of the 27 March 2013 Nantou Taiwan earthquake using modified semi-empirical approach

“…Second method of simulation is stochastic simulation of high-frequency strong ground motion which is given by Housner and Jennings (1964), Hanks and McGuire (1981), Boore (1983), Boore and Atkinson (1987) and Lai (1982). Third method is empirical green's function (EGF) method given by Hartzell (1978Hartzell ( , 1982, Kanamori (1979), Hadley and Helmberger (1980), Mikumo et al (1981), Irikura and Muramatu (1982), Irikura (1983Irikura ( ,1986, Irikura and Kamae (1994), Munguia and Brune (1984) and Hutchings (1985). Among all of the above methods of simulation empirical green's function (EGF) technique is most reliable simulation method for simulation of strong ground motion data.…”

“…Among all of the above methods of simulation empirical green's function (EGF) technique is most reliable simulation method for simulation of strong ground motion data. This method was initially introduced by Hartzell (1978), and modification in this technique has been made by Kanamori (1979), Irikura (1983), Munguia and Brune (1984) and Irikura (1986). In empirical green's function (EGF) technique, the major limitation is the requirement of aftershock event at every respective site of simulation.…”

A Simplified Technique for Simulating Wide-band Strong Ground Motion for Two Recent Himalayan Earthquakes

“…The method does not require aftershocks of the main event at a specific station as required by the EGF technique by IRIKURA (1986), HARTZELL (1978HARTZELL ( , 1982, KANAMORI (1979), HADLEY and HELMBERGER (1980), MIKUMO et al (1981), IRIKURA and MURAMATU (1982), IRIKURA (1983IRIKURA ( , 1986, KAMAE and IRIKURA (1998), MUNGUIA and BRUNE (1984) and HUTCHINGS (1985). It also does not require detailed velocity Q structure and complete source mechanisms as required in the method of composite source modelling by ZENG et al (1994), YU (1994), YU et al (1995), SAIKIA and HERRMAN (1985) and SAIKIA (1993).…”