1999年9月14日、11月30日在四川省绵竹县清平乡和汉旺乡先后发生5.0级地震。两次地震活动时间相隔两个多月。微观震中相距29km，宏观震中只相距12km，两
两次MS5.0级地震属双震。
两次MS5.0级地震的宏观震中分别位于四川省绵竹县清平乡和汉旺乡，两次地震的烈度均达Ⅵ度，极震区均为北北东向椭圆，烈度超过Ⅵ度的面积分别为60km2和7km2。两次地震共造成1人死亡，2人受重伤，5人受轻伤，总经济损失为813万元人民币。
两次地震的震源机制解结果表明：9月14日的5.0级地震是在北西西向近水平主压应力作用下，产生的一次逆冲型错动；11月30日的5.0级地震是在近南北向主压应力作用下，产生的一次兼有逆冲分量的右旋走滑错动。两次地震的地震断裂面为北东方向，与龙门山断裂带总体走向一致。
距两次地震震中200km范围内（取两次震中经纬度中值31.5°N、104.2°E为圆心），共有23个地震台，其中开展测震观测台18个（包括成都模拟遥测台网8个子台），前兆观测台14个。有地下水位、水氡、地磁、地电阻率、地倾斜、重力、跨断层短水准等24个前兆观测台项。两次MS5.0级地震前的龙门山小地震活动均有增强，第一次在震区西南侧发生大邑ML3.8级地震（1999年9月8日）；第二次同样在震区西南侧发生大邑ML3.7级地震（1999年11月16日）。定点前兆观测异常方面，震前出现一些中期异常，在中期异常的背景上，出现短期异常。
9月14日绵竹清平5.0级地震前，四川省地震局和有关市、县地震部门未作短临预测。11月30日的绵竹汉旺5.0级地震前，四川省、市、县地震部门根据震前所掌握的异常情况，尤其是区域地震活动性异常，提出短临预测意见。德阳市地震局以及绵竹县地办均分别向当地政府领导作了汇报，当地地震部门和各级地方政府采取了积极稳妥的应对措施，极大减轻了第二次5.0级地震造成的社会影响。
Abstract
On Sept. 14 and Nov.30, 1999, 2 earthquakes of MS5.0 occurred one after another in Qingping and Hanwang, Mianzhu County, Sichuan province. The distance between the 2 epicenters determined by seismometers was 29 km. And the distance between the 2 macroseismic epicenters determined by the field investigations was 12 km. The 2 earthquakes of MS5.0 were considered as double earthquakes.
The seismic intensities of two earthquakes were Ⅵ. The meizoseismal areas were oval in shape with major axes in NNE direction. The areas of 2 meizoseismal areas of intensity larger than Ⅵ were 60 and 7 km2 respectively. The 2 earthquakes killed 1 person, heavily injured 2 and lightly injured 5. The total economic loss was about 8.13 million Yuan (RMB).
The focal mechanism solutions of the 2 earthquakes show that (1) the MS5.0 earthquake on Sept. 14, 1999 was caused by right lateral movement on a trust fault under the action of nearly horizontal stress in NWW direction; (2) the MS5.0 earthquake on Nov. 30, 1999 was caused by right lateral strike slip and thrust slip on the fault under the action of compressive stress in nearly NS direction. The directions of the rupture planes of both earthquakes were NE and generally parallel to the Longmenshan Mountain fault.
Within 200 km from the middle position (N31.5°，E104.2°) of the epicenters, there were 23 seismic stations. Among them there were 18 seismometric stations (include 8 stations in the Chengdu Telemetric Network) and 14 precursory observation stations, with 4 observation items on groundwater level, randon content in groundwater, geomagnetism, apparent resistivity, crustal deformation, short route leveling and gravity. Before the MS5.0 earthquakes, there were anomalous activity of small shocks in the Longmenshan region. Before the first MS5.0 earthquake the Dayi Earthquake of ML3.8 on Sept.8, 1999 occurred southwest to the epicenter of the mainshock，and before the second MS5.0 earthquake another Dayi earthquake of ML3.7 on Nov. 16, 1999 occurred at the same place. For the precursory observations，there were some mid-term anomalies and some short-term anomalies superposed on the background of the mid-term anomalies.
The Seismological Bureau of Sichuan province and the seismological agencies of the local city and county governments did not make any short term and imminent predictions before the Qingping MS5.0 Earthquake on Sept.14, 1999. But based on the precursory anomalies and especially the anomalies in seismic activities in the local region, the seismological agencies of the province, the city and the county made a short term and imminent prediction. At the same time the Seismological Bureau of Deyang City and Seismological Office of Mianzhu County reported the seismic situation and the prediction to the local government leaders. Some positive measurements against the earthquake were taken by the local seismological agencies and local governments and they greatly reduced the panic of the society caused by the second earthquake.