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我们综合大地测量、地质和地震的信息估算了三类地震构造区中破坏性地震的频度。A类区包含的断层有足够的古地震资料来估算条件概率。B类区内有断层,但没有足够的数据进行条件概率分析。C类区包含各种或隐伏断层。假定每类区中都有随机分布的地震加上特定断层上的特征地震。我们的“串联”模型可用于多段断层的地震。在每一区中,散布的地震被假定为时、空均匀的,并遵从截头的古登堡—里克特震级分布。因此,地震危险性就由特征地震发生率、所有散布地震的发生率以及极限(特征)震级来定义。极限震级视断层长度确定,而地震发生率决定于地震活动性和地震矩率。我们提出了一个优选的基于对数正态重复的地震危险性模型和一个待选的泊松模型。这些模型预测,在南加州2024年前发生一个m≥7的地震的发生概率为80％至90％。1994年1月17日北里奇地震覆盖了南加州13％的面积,它的矩速率密度最高。2024年前在文图拉和圣贝纳迪诺地区0.2g或更大地震动的概率超过60％,在圣巴巴拉和圣贝纳迪诺之间的整个横断山脉的概率超过50％。预测的地震活动性超过历史上观测的地震活动性。这可能意味着(1)我们低估了最大震级,(2)大量的应变可能以非地震形式释放了,或者(3)自1850年以来地震活动性处于非正常的低潮。
Based on geodetic, geologic and seismic information, we estimated the frequency of destructive earthquakes in the three types of seismic tectonic zones. Class A areas contain faults that have sufficient paleoseismic data to estimate the conditional probability. There is a fault in zone B, but there is not enough data for conditional probability analysis. Zone C contains various or hidden faults. It is assumed that there is a random distribution of earthquakes in each type of area plus the characteristic earthquakes on a particular fault. Our “tandem” model can be used for multi-section fault earthquakes. In each zone, scattered earthquakes are assumed to be time-space-uniform and follow the Gutenberg-Richter magnitude distribution. Therefore, the danger of earthquakes is defined by the occurrence rate of characteristic earthquakes, the incidence of all scattered earthquakes and the magnitude of the limit (characteristic). The ultimate magnitude depends on the length of the fault and the occurrence of the earthquake depends on the seismicity and the seismic moment. We propose a preferred earthquake hazard model based on log-normal recurrence and a Poisson model to be selected. These models predict the probability of earthquakes of m ≥ 7 occurring in southern California by 2024 to be 80% to 90%. The Northridge earthquake covered 13% of Southern California’s area on January 17, 1994, with the highest moment-rate density. The probability of a 0.2g or greater earthquake in Ventura and San Bernardino regions before 2024 surpassed 60%, with a probability of exceeding 50% over the entire cross-mountain range between Santa Barbara and San Bernardino. The predicted seismic activity exceeds the historical observed seismicity. This may mean that (1) we have underestimated the maximum magnitude, (2) a significant amount of the strain may have been released in the form of non-earthquakes, or (3) the seismicity has been abnormally low since 1850.