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对最近5a新提出的北美东部(ENA)的地面运动关系进行了研究,将Atkinson和Boore(1995)的经验-随机关系,由电力研究所(EPRI,1993;Toro et al., 1994)、Frankel等(1996)研究得出的关系,及由SSHAC(1996)公布的北美东部标准地面运动数值作了比较。我们与EPRI或Frankel的关系之间存在的主要差别表现在低频振幅上(f<2Hz,包括所有震级)。应用我们的经验震源模型,在1Hz处得出的振幅比用Brune的单拐角频率得出的值低(至少1/2)。使用经验模型是为了使结果与ENA地面运动数据库尽可能相近。同时我们把加州经验关系式与新的ENA关系式作了比较。由于要获得典型的加州土壤条件下的等效地面运动,需要校正ENA的硬岩地面运动,因而二者之间的比较交得更为复杂。由进行该校正时所用的两种可选择的方法产生了相应的不同结论。一种可能结论是:由我们的ENA关系式得出的加州低频振幅与Boore等(1993,1994)及Abrahamson和Silva(1996)得出的类似,但在高频得出的ENA振幅远大于(大于2倍因子)加州的值。可选择的土壤校正得出的结论是:由我们的ENA关系式得出的值在低频稍低于(低于2倍因子)由加州关系得出的值,而在高频较高。上述两个结论均表明:某一地区的地面运动关系或地震的时间序列不能作简单修改就在其他地区的工程评估中使用。
The recent 5-A proposed ground motion of the ENA in North America was studied. The empirical-random relationship between Atkinson and Boore (1995) was studied by the Electric Power Research Institute (EPRI, 1993; Toro et al., 1994) Et al. (1996) and the North American East Standard Ground Motion Values published by SSHAC (1996). The main difference between our relationship with EPRI or Frankel is at low frequency amplitudes (f <2Hz, including all magnitude). Using our empirical source model, the amplitude at 1 Hz is lower (at least ½) than the value obtained using Brune’s single-corner frequency. Empirical models are used to make the results as close as possible to the ENA ground-motion database. At the same time we compare the California empirical relationship with the new ENA relationship. Comparisons between the two are more complicated due to the need to calibrate ENA’s hard rock ground motion for equivalent ground motion under typical California soil conditions. The two alternative approaches used to make this correction produce correspondingly different conclusions. One possible conclusion is that the California low-frequency amplitude derived from our ENA correlation is similar to that obtained by Boore et al. (1993, 1994) and Abrahamson and Silva (1996), but the amplitude of ENA at higher frequencies is much larger than Greater than 2 factor) California value. Alternative soil correction leads to the conclusion that the values derived from our ENA relationship are slightly lower (less than 2 times the factor) from the California relationship at low frequencies and higher at higher frequencies. Both of the above conclusions show that the ground motion in a certain area or the time series of earthquakes can not be easily modified to be used in engineering assessment in other areas.