Remote sensing anomalies of multiple geospheres before the Wenchuan earthquake and its spatiotemporal correlations

The preparation for the occurrence of an earthquake is a complicated process. This process is usually accompanied with material migration, energy release, and information exchange, which can disturb the radiation balance in the seismogenic zone. Obtaining the changing information of the coversphere, atmosphere, and ionosphere through satellite remote sensing; analyzing seismic anomalies; and identifying earthquake precursors, have become the interactive hotspots of the remote sensing and seismology fields. As a typical case where numerous anomalies precede the main shock, this study investigated the Ms 8.0 Wenchuan earthquake and its physical mechanism of the relevant seismic anomalies. On the basis of published research results, this study systematically collected and filtered the possible remote sensing anomalies of the Wenchuan earthquake under certain criteria and summarized the abnormal features of 20 remote sensing parameters related to the coversphere (five parameters), atmosphere (eight parameters), and ionosphere (seven parameters). By mapping the anomalies in a unified framework, the spatiotemporal correlations among the anomaly manifestations were analyzed, and the overall spatiotemporal characteristics of the short-term manifestations of multiple anomalies were revealed. The results of this study can be summarized as follows. (1) The manifestations of remote sensing anomalies gradually increased, enhanced, and congested before the Wenchuan earthquake, and prominent impending earthquake precursors were observed. (2) Remote sensing anomalies developed in a bottom-up manner from the coversphere and atmosphere to the ionosphere three months before the shock, which is in accordance with the Lithosphere-Coversphere-Atmosphere-Ionosphere (LCAI) coupling paradigm. (3) Strong spatial correlations were present among the seismic faults and manifestation positions of short-term-to-impending remote sensing anomalies, which congested along the Longmenshan faults and its nearby region. (4) Multiple short-term-to-impending remote sensing and strip-shaped anomalies covered the epicenter of the main shock and developed along the Longmenshan faults, respectively, thereby reflecting the local effect of the LCAI coupling in the late stage of the seismogenous process. The clustering multi-parameter remote sensing anomalies before May 12 can be regarded as Wenchuan earthquake anomalies with precursory significance. At the macroscopic scale, the seismic response driven by the deep part of the Earth can be explained using the knowledge on the multiple geosphere coupling of the entire planet system. The in-depth analysis of the individual characteristics, spatiotemporal correlations, and overall laws of the Wenchuan earthquake remote sensing anomalies during the earthquake preparation process is critical to the investigation of the physical mechanism of seismic anomalies. This retrospective research provides heuristic clues about the energy exchange process of the Wenchuan earthquake and confirms the great potential of multi-parameter earthquake precursor research. Furthermore, this study benefits the satellite monitoring and synergic analysis of strong inland earthquakes during the late stage of earthquake preparation and provides reference for earthquake prediction studies. © 2020, Science Press. All right reserved.