The November 14, 2001 west of Kunlun Mountain Pass earthquake: An earthquake with unsaturated surface wave magnitude

Abstract

This paper presents an overview of the magnitude determination of the November 14, 2001 west of Kunlun Mountain Pass (KMP) earthquake at the juncture of Xinjiang and Qinghai, northwestern China. Comparisons are made among surface wave magnitudes determined by China National Digital Seismograph Network (CNDSN), National Earthquake Information Center (NEIC) of US Geological Survey (USGS) and moment magnitudes determined by different institutions in China and abroad. The result shows that different institutions yield different surface wave magnitudes, as different data and calculation formulae are used in magnitude determination. The magnitude of the earthquake in China’s Rapid Earthquake Information Release was given as MS=8.1; measurement given in the formally edited and published Observation Report of China Digital Seismograph Network is MS=8.2; and magnitude determined by USGS/NEIC is Ms=8.0. Soon after the occurrence of the KMP earthquake, Harvard University (Harvard), USGS/NEIC, Earthquake Research Institute, Tokyo University (ERI), Center for Analysis and Prediction, China Earthquake Administration (APCEA) and Institute of Geophysics, China Earthquake Administration (IGCEA) gave the moment magnitude MW as 7.8, 7.7, 7.7, 7.6 and 7.5, respectively, based on data from Global Seismograph Network (GSN), CNDSN and China Digital Seismograph Network (CDSN). These measurements, with an average value of MW=7.7, are close to each other. As moment magnitude is a physical quantity measuring the absolute size of an earthquake and has obvious advantages over conventional magnitude scale, and is the preferred magnitude of the international seismological community. It is concluded that the KMP earthquake is an earthquake with unsaturated surface wave magnitude with moment magnitude MW=7.7 and surface wave magnitude MS=8.0.