基于时空联合的震前热异常提取方法研究

Research on Pre-earthquake Thermal Anomaly Extraction Method Based on Spatiotemporal Combination

震前热红外辐射异常现象已成为评估区域地震危险性的重要参考指标。然而, 地表热辐射受大气辐射、地形、天气等多种因素的影响, 从中准确识别由构造活动引发的热异常仍是一项具有挑战性的研究。当前的震前热异常提取方法大多仅仅考虑时间域或者是空间域分析, 难以同时考虑时空特征。为此, 本文提出了一种兼顾时间特征和空间特征的震前热异常提取模型, 该模型包括原地温度的提取、原地涡度的计算、多年背景场影响的消除以及热异常的判定。采用MODIS LST数据, 就和田地震及尼泊尔地震发生前的热异常进行了提取和分析, 研究结果表明: (1) 提取的震前热异常在时空分布上与构造活动具有显著关联; (2) 地震年份的地壳活动相比非震年份更为强烈, LST异常更显著; (3) 震前热异常的变化并不单一, 而是呈现出周期性的强弱交替, 并在空间上反复波动。本文研究可为震前热异常的识别及地震监测提供新的方法支持和理论参考。

The pre-earthquake thermal infrared radiation anomaly has become an important reference index for assessing regional seismic hazard. However, the surface thermal radiation is affected by various factors such as atmospheric radiation, topography and weather, making it a challenging research to accurately identify the thermal anomalies caused by tectonic activities. Most of the current pre-earthquake thermal anomaly extraction methods only consider time-domain or spatial-domain analysis, and it is difficult to simultaneously consider the spatio-temporal characteristics. Therefore, this paper proposes a pre-earthquake thermal anomaly extraction model that takes into account both temporal and spatial features. The model includes the extraction of in-situ temperature, the calculation of in-situ vorticity, the elimination of the influence of the multi-year background field, and the determination of thermal anomalies. Using MODIS LST data, the pre-earthquake thermal anomalies of the Hotan earthquake and the Nepal earthquake were extracted and analyzed. The research results show that: (1) The extracted pre-earthquake thermal anomalies have a significant correlation with tectonic activities in terms of spatio-temporal distribution; (2) The crustal activities in the earthquake year are more intense than those in the non-earthquake year, and the LST anomalies are more significant. (3) The changes in pre-earthquake thermal anomalies are not uniform, but show periodic alternation of strong and weak, and fluctuate repeatedly in space. The research in this paper can provide new method support and theoretical reference for the identification of pre-earthquake thermal anomalies and earthquake monitoring.