A New Concept of Intensity Data Area and Its Effect on the Parameter Determination of Historical Earthquakes

Abstract

Abstract In ancient China, the government annals provided abundant historical earthquake records, which lasted more than 2000 yr. In some cases, the earthquake damage descriptions from the high-tier government annals are so concise that the specific place names were omitted, even the names of towns where the damage might have actually occurred. The intensity data point (IDP) was assigned to the capital town of the high-tier government, which might lead to large uncertainties in the historical earthquake parameters. A new concept of intensity data area (IDA) is proposed specifically to deal with this issue. An approach on how to convert the IDA to an IDP, based on nonseismological information, is described. In this process, we emphasize the effectiveness of field trips to investigate local features, such as natural environment, population distribution, historical administration zoning, and so forth. As case examples, two historical earthquakes in the Ming Dynasty are analyzed. The documentations of both earthquakes have a common problem, in that some damage was described with the name of the highest-tier local government (Fu); this led to the dispute about the parameter of historical earthquakes. With the proposed method, the IDA for Fu is successfully converted to an IDP at the suitable site. This is the key step to solve the dispute and reduce the parameter uncertainty. Our results have revealed that the parameters of both case earthquakes in the latest edition of the catalog (“The Catalog of Chinese Historical Strong Earthquakes (2300 B.C.–A.D. 1911)”) were wrong (Min et al., 1995). It is noteworthy that the latest edition of the catalog is currently in common use. To avoid the misuse of the catalog, it is better that the parameters in the catalog be restudied, especially for those labeled with large uncertainties.