利用GPS连续观测资料进行强震危险性预测的探讨
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摘要
中国地壳运动观测网络基准站自1999运行以来已经积累了8年多的观测资料,目前针对地震预测、观测对象和数据处理方法,广义地提出了"点、线、面"的分析方法。实际应用表明,利用"线"的分析方法可能是比较好的方法,它最大的优点是在恰当的空间范围内不但可降低噪声,而且可突出异态信息。在目前较低测控能力的基础上,可通过全空间扫描与现象分析发现:①距昆仑山口西地震震中最近的德令哈观测站相对于拉萨观测站在震前较早的时间,其EW向就出现了缓慢变化,乃至闭锁(或无差异变化),直至地震发生为止,持续时间超过2年,闭锁数值10 mm以上,震后恢复正常;②云南地区数次强震震前下关观测站相对于泸州观测站EW向出现了闭锁或低于正常的变化,2003年强震之后恢复正常;最近的普洱强震自2006年初EW与SN向均出现了相对闭锁,两个方向的数值分别接近和达到10 mm;此外,每阶段异常的持续时间均超过1年;③塔什—乌什间EW向在新疆巴楚地震前出现了闭锁性活动,时间2年以上,数值约10 mm,震后恢复正常;目前SN向有相对闭锁迹象,并正在趋于明朗;④鼎新—西宁间EW方向有相对闭锁的迹象,但时间尚短;⑤通过寻找相对"闭锁"区段有可能成为判定强震危险性存在与否的主要方法。由此推测,若普洱6.4级地震后闭锁不解除,川滇菱形块体的西边界构造带及周围地区仍是近期强震最有可能发生的地区,其次是新疆的西天山地区,目前青藏高原东北缘尚不明朗。
The observational data for more than 8 years have been accumulated since the reference stations of the Project of "China Crust Movement Measuring Network" run in 1999,now the analytical method of "point,line and surface" is generally proposed aiming at seismic prediction,observation object and the means of data processing.The practical application suggests that taking use of "line" maybe a kind of comparatively good method,whose best strongpoint is not only reducing noises in proper scale of space,but also giving prominence to the exceptional information.Based on the foundation of the relatively low power of measuring and surveying,and through the whole space scanning and phenomenon analyzing,we discover: ① Relative to Lasa station,Delingha station,the nearest one to the epicenter of Kunlun Mountain earthquake,appeared slow variation,even atresia(or no differential variation),in the EW direction early before the earthquake,and the atresia ended until the earthquake occurrence,the lasting time exceeded 2 years,the atresia magnitude was more than 10mm,while after the earthquake it resumed the normal status;② Before several strong earthquakes in Yunnan region,Xiaguan station,relative to Luzhou station appeared atresia or variation that was lower than the normal level in the EW direction,after the strong earthquake in 2003,it resumed the normal status;In the latest Pu'er earthquake it has appeared relative atresia in both the EW and SN directions since the beginning of 2006,the magnitude of every direction approaches and reaches 10mm respectively;Besides,the lasting time of anomaly of every stage all exceed 1 year;③ The EW direction of Tashi-Wushi appeared atresic activity before Bachu earthquake in Xinjiang,and the lasting time was more than 2 years,the magnitude was about 10mm,while after the earthquake it resumed the normal status;At the present time,the SN direction has the evidence of relative atresia,and which is inclining to be clear;④ The EW direction of Dingxin-Xining has the evidence of relative atresia,but the lasting time is comparatively short;⑤ The method of searching for section of relative "atresia" maybe become the main approach for determining the risk of strong earthquakes.Thus,it can be inferred that if the atresia was not relieved after Pu′er M_S6.4 earthquake,the tectonic zone of the west boundary of Sichuan and Yunnan diamond block and its surrounding regions is still the potential area for occurrence of strong earthquakes recently.The second risk area might be is the west area of Tianshan in Xinjiang,but the northeast boundary of Qingzang plateau is not clear at present.
The observational data for more than 8 years have been accumulated since the reference stations of the Project of "China Crust Movement Measuring Network" run in 1999,now the analytical method of "point,line and surface" is generally proposed aiming at seismic prediction,observation object and the means of data processing.The practical application suggests that taking use of "line" maybe a kind of comparatively good method,whose best strongpoint is not only reducing noises in proper scale of space,but also giving prominence to the exceptional information.Based on the foundation of the relatively low power of measuring and surveying,and through the whole space scanning and phenomenon analyzing,we discover: ① Relative to Lasa station,Delingha station,the nearest one to the epicenter of Kunlun Mountain earthquake,appeared slow variation,even atresia(or no differential variation),in the EW direction early before the earthquake,and the atresia ended until the earthquake occurrence,the lasting time exceeded 2 years,the atresia magnitude was more than 10mm,while after the earthquake it resumed the normal status;② Before several strong earthquakes in Yunnan region,Xiaguan station,relative to Luzhou station appeared atresia or variation that was lower than the normal level in the EW direction,after the strong earthquake in 2003,it resumed the normal status;In the latest Pu'er earthquake it has appeared relative atresia in both the EW and SN directions since the beginning of 2006,the magnitude of every direction approaches and reaches 10mm respectively;Besides,the lasting time of anomaly of every stage all exceed 1 year;③ The EW direction of Tashi-Wushi appeared atresic activity before Bachu earthquake in Xinjiang,and the lasting time was more than 2 years,the magnitude was about 10mm,while after the earthquake it resumed the normal status;At the present time,the SN direction has the evidence of relative atresia,and which is inclining to be clear;④ The EW direction of Dingxin-Xining has the evidence of relative atresia,but the lasting time is comparatively short;⑤ The method of searching for section of relative "atresia" maybe become the main approach for determining the risk of strong earthquakes.Thus,it can be inferred that if the atresia was not relieved after Pu′er M_S6.4 earthquake,the tectonic zone of the west boundary of Sichuan and Yunnan diamond block and its surrounding regions is still the potential area for occurrence of strong earthquakes recently.The second risk area might be is the west area of Tianshan in Xinjiang,but the northeast boundary of Qingzang plateau is not clear at present.
引文
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[6]顾国华.印尼8.7级大震前后GPS观测站的地壳水平与垂直位移时间序列结果[J].地震,2006,26(2):19-28.
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[8]吴云,孙建中,乔学军,等.GPS揭示的现今地壳运动与地震前兆特征[J].大地测量与地球动力学,2003,23(3):14-20.
[9]王琪,张培震,牛之俊,等.中国大陆现今地壳运动与构造变形[J].中国科学(D辑),2001,31(7):529-536.
[2]杨国华,张风霜,武艳强,等.GPS基准站坐标分量噪声的时间序列与分类特征[J].国际地震动态,2007,(7):80-86.
[3]皇甫岗,石绍先,苏有锦.20世纪云南地区地震活动研究[J].地震研究,2000,23(1):1-9.
[4]敬少群,王佳卫,吴云,等.用GPS时间序列获取中国大陆微动态应变场[J].地震学报,2006,28(5):478-484.
[5]敬少群,吴云,乔学军,等.GPS时间序列及其对昆仑山口西8.1级地震的响应[J].地震学报,2005,27(4):394-401.
[6]顾国华.印尼8.7级大震前后GPS观测站的地壳水平与垂直位移时间序列结果[J].地震,2006,26(2):19-28.
[7]顾国华,张晶,王武星.中国地壳运动观测网络基准站水平位移向量时间序列[J].地震,2003,23(2):39-47.
[8]吴云,孙建中,乔学军,等.GPS揭示的现今地壳运动与地震前兆特征[J].大地测量与地球动力学,2003,23(3):14-20.
[9]王琪,张培震,牛之俊,等.中国大陆现今地壳运动与构造变形[J].中国科学(D辑),2001,31(7):529-536.
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