Surface latent heat flux anomalies preceding inland earthquakes in China

Using data from the National Center for Environmental Prediction (NCEP), the paper analyzed the surface latent heat flux (SLHF) variations for five inland earthquakes occurred in some lake area, moist area and arid area of China during recent years. We used the SLHF daily and monthly data to differentiate the global and seasonal variability from the transient local anomalies. The temporal scale of the observed variations is 1-2 months before and after the earthquakes, and spatial scale is about 10°×10°. The result suggests that the SLHFs adjacent the epicenters all are anomalous high value (>μ+2σ) 8-30 days before the shocks as compared with past several years of data. Different from the abnormal meteorological phenomenon, the distribution of the anomalies was isolated and local, which usually occurred in the epicenter and its adjacent area, or along the fault lines. The increase of SLHF was tightly related with the season which the earthquake occurs in; the maximal (125 W/m², Pu'er earthquake) and minimal (25 W/m², Gaize earthquake) anomalies were in summer and winter, respectively. The abundant surface water and groundwater in the epicenter and its adjacent region can provide necessary condition for the change of SLHF. To further confirm the reliability of SLHF anomaly, it is necessary to explore its physical mechanism in depth by more earthquake cases.