Passive microwave response associated with two main earthquakes in Tibetan Plateau, China

The thermal anomalies associated with earthquakes using satellite infrared data are being studied in different parts of the world for more than three decades. The thermal anomalies have emerged as one of the potential earthquake precursor. However, often cloud cover obstructs detection of the thermal anomalies. Compared to infrared, passive microwave sensors provide information about the thermal radiations under any weather conditions. In the present study, we have carried out detailed analysis of brightness temperature data derived from the Defense Meteorological Space Program (DMSP) Special Sensor Microwave/Imager (SSM/I) to determine thermal anomalies associated with the 1997 Manyi and 2001 Kokoxili earthquakes. Brightness temperature data for 13 years period from 1996 to 2008 observed from F13 satellite were considered to avoid difference in the sensor sensitivity. Based on 9 years background data that ignoring data for the years in which strong earthquake occurred, we computed Index of Microwave Radiation Anomaly (IMRA) over the Manyi-Yushu Fault (MYF) and Kun Lun Fault (KLF) zones, Tibetan Plateau. Our results indicate that the microwave brightness temperature at 19.35 GHz has higher sensitivity to the seismic anomalies in comparison to the other higher frequency channels. The IMRA with multi-region, multi-frequency, and multi-parameter variation were analyzed to validate our results. In addition, variation of different parameters (microwave brightness temperature, near surface air temperature and carbon monoxide-CO) observed for Kokoxili earthquake shows the transfer process of thermal anomalies from the focal region to the atmosphere during the preparation and occurrence of earthquake. Passive microwave satellite data combined with other surface and atmospheric parameters provide better understanding of physical mechanism of thermal anomalies associated with earthquakes.