摘 要 GPS用于地震监测预报的研究在我国最早开始于20世纪80年代，但当时只限于引进少量设备进行试验、引进技术进行消化和研究。随着GPS观测精度的提高和硬件成本的不断降低，到90年代陆续建立了若干GPS区域网络，开始了较为系统的GPS监测、数据处理和应用的研究。本文简要介绍3个将GPS用于地震监测预报研究的实例：
1. 印度洋8.7级特大地震后对我国地震趋势的判定
中国地壳运动观测网络分别于1999、2001、2004年进行了3次复测。2004年12月26日发生了印尼Ms8.7级特大地震，我国川滇地区震时和震后有明显的响应，如小震活动加强，流体等各种前兆异常突出等等。为了判定我国大陆地震活动趋势，对川滇地区进行紧急GPS应急加测。在以前三期复测资料研究的基础上，对这次紧急复测资料和相关的几个GPS连续观测站的资料进行了分析和研究。经本文的研究得到以下几点看法和结论：（1）印度洋8.7级地震震时和震后一段时间内对我国的川滇藏地区的形变有一定的影响，但主要是机械振动所致。（2）通过对GPS资料的多种方法分析后认为，我国南北带南部的地壳形变在印度洋8.7级地震震时和震后一段时间内呈相对松弛变化。（3）这种变化有利于在较短的时间内触发5-6级中强地震。（4）在应力场未进一步加强之前，孕育发生7级以上强震的可能性不大。以上判断到目前仍是正确的。
2. 对昆仑山8.1级大震的中长期预测
在中国地震局“九五”中长期地震预测研究重点项目中，通过对各种形变资料的应用研究在全国范围内于1998年给出了13个强震危险区，东部6级以上，西部7级以上。其中第5号危险区正好位于昆仑山8.1级大震的发震破裂之上。该区域缺少各种前兆观测资料，1994-1996年Q14-Q15号GPS点之间较大幅度的缩短变化是划定该危险区的主要证据之一。顺便指出，武汉（Q02）到厦门（Q03）之间的GPS基线在1994-1996年间也出现了最为显著的缩短变化，当时认为是菲律宾板块挤压所致，若有地震应该在台湾地区发生。由于当时笔者负责的科研项目是针对大陆强震中长期预测的研究，同时又缺少台湾地区的相关资料，故没有对台湾地区的强震危险性进行预测。后来于1999年9月21日发生了台湾Ms7.4级的集集大地震，现在看来，武汉到厦门GPS长基线的异常缩短可能对这次地震有一定的指示意义。
3.对2005年2月15日新疆乌什Ms6.2级地震的年度预测
在中国地震局“十五”中期预测研究项目的阶段性研究结果中，利用地倾斜前兆变化分布的空间配套特征，在乌鲁木齐西部给出了一个6级左右的中期地震危险区预测，2004年实施了中国地壳运动观测网络的第三次复测，于2004年十月对全部GPS资料进行了处理，结果发现，巴楚-阿克苏附近存在的水平差异运动显著，最大剪应变出现高值，附近有柯坪断裂发育，属地震多发构造，与地倾斜给出的地震危险区较近，据此，通过会商，在中国地震局第一监测中心2005年年度震情趋势研究报告中，将胜利达板-开都河地震中期危险区调整到巴楚-阿克苏附近，并将中期危险区升级为年度地震危险区，预测震级为6级左右。时间、地点、震级对应的均比较好。
本文认为，地震预测尚未过关，是复杂的世界性科学难题，但我们在多年的实践探索中也确实取得了一定的进展，值得总结。
Abstract The earliest researches on application of GPS to earthquake monitoring and prediction in China began in1980s, and it was limited to learn some relative technology from other countries and do some test with a few of equipments. As the improvement of software for data processing and the depreciating of hardware, several local GPS network had been set up till the end of 1990s, and then more systematically GPS monitoring, data processing and its application research have been done gradually. In this paper, 3 research examples of the application of GPS to earthquake monitoring and prediction are presented.
1. The judgment of earthquake situation in China after the great earthquake with Ms8.7 in The Indian Ocean.
Three repetitions of GPS measurement on China Crust Movement Observation Network were done respectively in 1999, 2001 and 2004. 26 Dec,2004, the Indonesia great earthquake with Ms8.7 occurred. At the same time, in the region of Yunnan and Sichuan of China, a series of anomalies appeared, such as the intensifying of earthquake activity, ground water anomalies, etc. For judging the earthquake situation in this region, the regional GPS network re-measurement was done from Jan to Feb, 2005. Based on the former researches, all the re-measurement GPS data and the GPS data from a few of relatively continuous observation stations are processed and studied. A few points are given as follows: (1) The Indonesia great earthquake with Ms8.7 induced some crust deformation in the region of Yunnan, Sichuan and Tibet at the quake time and a period after that, but the deformation was induced mainly by mechanic vibration. (2) Processing the GPS data in different way, it shown us that crust deformation in the region of Yunnan and Sichuan of Chin was relatively loosening in the period after the great quake. (3) Such a deformation is favorable to trigger quake with Ms5-6 in a short period. (4) Before the further strengthening of crust stress, it seems impossible to generate a earthquake stronger than Ms7. The judgments above are also correct at present
.
2. Long- and medium-term prediction of Kunlunshan Ms8.1 earthquake
Through research on various crust deformation data in China for the key task of CEA for long- and medium-term earthquake prediction in the period from 1996 to 2000, 13 strong earthquake dangerous areas were given with Ms≥6 in East China and Ms≥7 in West China in which the No.5 dangerous area just located on the rupture of Kunlunshan Ms8.1 earthquake. There are short of precursory observation data in this area, and the main evidence for the dangerous area is the obviously shortening of the GPS baseline from Q14 to Q15 in 1994-1996. By the way, in the same time the GPS baseline from Wuhan(Q02) to Xiamen(Q03) was also shortened greatly. We thought it was induced by the push of Philippine block, and if there were an earthquake, it would occur in Taiwan. Because our task was focusing on the main continent and there was lack of relative data from Taiwan, there was no prediction for Taiwan area. Afterwards, the great Jiji earthquake with Ms7.4 occurred on 21 Sep, 1999. It seems that the shortening of baseline of Q02-Q03 implied something for the earthquake.
3. The yearly prediction of Wushi Xinjiang earthquake with Ms6.2 occurred on 15 Feb,2005
In the stage work of CEA for earthquake medium-term prediction research in the period of 2001-2005, an earthquake dangerous area with Ms=6 was given in the west of Wulumuqi with earth tilt data in 2003. The third re-measurement of China Crust Movement Observation Network was made in 2004, and all the GPS data were processed till Oct 2004. The result shown that there were obvious different level movement between different GPS stations near Bachu-Akesu area, and the Maximum of shear strain appeared as high value. It is a prone-earthquake area, not far from the dangerous area above mentioned, and there is Keping fault here. Through discussion, the dangerous area was moved from Shenglidaban-Kaiduhe to Bachu-Akesu area in 2005 yearly earthquake situation research report of First Crust Deformation Monitoring and Application Center, CEA, and the time scale was changed from medium-term to yearly, the predicted magnitude was also around 6. The location, time and magnitude are all correct.
Earthquake prediction is a complicated scientific problem in the world, and nobody can solve the problem perfectly yet. But some progresses have been made by practice and exploration for many years, and it is worth to give a summarization.
