基于天体引潮力周期变化的OLR异常初探

Preliminary Study on the OLR Anomalies Based on the Cycle Process of Celestial Tide Forces: A Case Study on the Xinyuan MS6.6 Earthquake

摘要:

采用NOAA卫星地面长波辐射（OLR）数据资料，数据空间分辨率为1°×1°、覆盖全球共360×181个格点，时间分辨率为1 d，时间起止为1954年至今。计算了2012年6月30日新疆新源6.6级地震天体引潮力变化和OLR逐日时空演化背景图像。结果表明：①本次地震发生在天体引潮力由高峰（6月20日）→低谷（6月30日）→高峰（7月5日）的周期变化过程由低谷向高峰时段，可能显示引潮力对发震构造的作用主要表现为加速断面的滑动。②+新源6.6级地震前后，亮温区域出现：起始→加强→高峰→衰减→平静→发震→小范围增温的变化过程，即6月25日在震中东北出现小范围的亮温现象，6月26日起亮温区域范围增大，强度增强，6月28日亮温异常范围和幅度减弱，6月29日亮温异常消失。6月30日发生了新源6.6级地震。而7月1日又出现亮温，可能与6月30日的6.6级地震及其后面余震的发生有关。该过程与岩石在受力破裂过程具有相似性，即岩石挤压→岩石微破裂→岩石破裂扩展→破裂终止等。

Abstract:

Earthquakes are definitely a mechanical phenomenon in which stress plays an important role.Many researchers have conducted statistical studies on the relationship between celestial tide forces (CTF) and earthquakes that prove that CTF may trigger earthquakes when the tectonic stress of the focal zone is at a critical stage.However，a method for identifying the critical stage point has not been determined thus far.Outgoing long-wave radiation （OLR） signals have been observed prior to strong earthquakes in recent years.OLR data describe the radiation information from the top of the atmosphere，which is believed to reflect energy changes in the earth-atmosphere system that occurs prior to earthquakes.OLR has characteristics of a large coverage range.Because earthquake-related anomaly information of OLR is extracted and applied to earthquake prediction，OLR anomalies are highly useful for areas that are out of the monitoring range of the current precursory seismic networks.Moreover, these anomalies are helpful for monitoring the stress stage of tectonics.In this study，we use National Oceanic and Atmospheric Administration （NOAA）satellite data to observe OLR data provided by the National Centers for Environmental Prediction （NCEP）with 1° × 1° resolution and attempt to analyze the OLR anomalies before and after the Xinyuan MS6.6 earthquake through the periodic variation effect of CTF.The earthquake occurred at a relativity high value of CTF，which it indicates that the CTF had a trigger effect on the earthquake. These results show that one month before the earthquake，no OLR anomalies were noted near the Xinyuan area.With the passage of time，the figures of spatio-temporal evolution of OLR increase were noted as initial rising on June 25 → continued rising on June 26 → reaching the peak on June 27 → weakening from June 28 to 29 → earthquake occurring on June 30.This evolution reflects the following activities of the seismic fault under tectonic stress：micro breaking-rupture strengthening → accumulating energy (the decrease of stress) → releasing energy → shaking. These abnormal areas moved and expanded，and the earthquake occurred at northeast edge of the anomaly；the epicenter of this earthquake was not at the area of maximum abnormality.This result may be related to the geological structure and underground environment of the epicenter.These characteristics can provide some clues for determining future seismogenetic times and for tracking the locations of the epicenters. It is necessary to combine the study of CTF with that of OLR anomalies to explore the catastrophic events of seismic faults under tectonic stress and to reveal the complex processes of the energy accumulated and released during an earthquake.We should emphasize that only considering the factors of CTF and OLR anomalies according to relative statistical analysis is insufficient for launching a theoretical model to predict the time and magnitude of future earthquakes in a particular region.The current understanding of the genetic mechanism of the anomalies for earthquakes is not complete； therefore，additional case studies are needed.