甘宁陕明代新增的十次中强历史地震

Ten New Added Moderate strong Historical Earthquakes Occured in Ming Dynasty in Gansu，Shaanxi and Ningxia Provinces

摘要:

历史上无破坏记载但影响面积较大的地震史料是历史地震学中的宝贵资料。本文通过对甘宁陕地区明代无破坏记载的历史中强震的史料考证、实地调查及对有感范围的统计计算，采用综合分析及类比的原则和方法，在前人的研究成果基础上又新确定补充了10次中强地震，并给出其基本参数。为研究区内完整的地震活动规律提供了新的科学依据。

Abstract:

The provinces of Gansu，Ningxia and Shaanxi are within the region where the Chinese nation originated.Earthquakes frequently occur in these provinces，but most of the region is vast，sparsely populated and far away from the state or county government centers of China.Local earthquake events in the region were not likely to be recorded completely in historical materials，especially if the epicenter was far from cities where it could be felt and reported.Therefore，historical data are likely to be limited and a large number of earthquakes may have been omitted from the records.Historic earthquakes，having their epicenter in the remote regions，may have been felt in cities but because of the distance between epicenter and detection it is difficult to objectively and quantitatively evaluate this historic earthquake activity.Further research on this part of historical data，aimed at more scientifically determining the basic parameters of the omitted moderate-strong historical earthquakes can contribute to a greater understanding of earthquake activity in this area. Improved objective analysis will help to define the social and economic benefits of safety evaluation for major engineering projects or disaster defense.In the study of historical earthquake data and field investigation in Gansu，Ningxia and Shaanxi provinces，we collected data related to ten moderate-strong historical earthquakes.We derived the basic parameters of each earthquake by comprehensive analysis，comparison，and statistical computing for the felt earthquakes.Seismic-tectonic activity in this region was then analyzed using the basic parameters.The strength of earthquakes was calculated using the following formulas：The relation between radius of equivalent circle of IV degree in western China and magnitude given by the Department of Seismic Hazard Prevention of State Seismological Bureau in 1995， is M=1.68lgR+2.24 （1） Where R is the radius of equivalent circle in kilometers and M is magnitude. In addition，another empirical formula given by Jiang Mei et al. （1997），is M=3.04lgRi-0.82 （2） Where Ri is the long radius of feeling area in Gansu，Ningxia and Qinghai provinces in kilometers and M is magnitude.In this study, the estimated magnitude is the average value of applying these two empirical formulas，which allows us to properly consider the local human environment and geographical conditions. The relation between magnitude M and intensity Ⅰ0 in Western China is M=0.605Ⅰ0+1.376 （3） Using this statistical formula，we calculated the intensities of each historical earthquake.The parameters of moderate-strong earthquakes in the Gansu，Ningxia and Shaanxi provinces for which no damage records are available could have important implications for understanding historic patterns and frequency of earthquakes in the region.Through detailed textual research that combines archaeology，science of historical materials，and geology we can develop the record of strong earthquakes that were previously omitted from the catalog for remote areas of northwest China.This can provide scientific and reliable data for seismological research and security of major constructions.