地球物理学进展 ›› 2020, Vol. 35 ›› Issue (4): 1299-1309.doi: 10.6038/pg2020CC0237

• 固体地球物理及空间物理学(大气、行星、地球动力学、重磁电及地震学、地热学) • 上一篇    下一篇

姑咱台的十年钻孔应变观测和汶川地震前兆异常

邱泽华(), 唐磊, 郭燕平, 张宝红   

  1. 中国地震局地壳应力研究所,北京 100085
  • 收稿日期:2019-09-28 修回日期:2020-04-23 出版日期:2020-08-20 发布日期:2020-09-02
  • 作者简介:邱泽华,男,1959年生,博士,研究员,主要从事钻孔应变观测技术研究. E-mail:qzhbh@163.com
  • 基金资助:
    国家自然科学基金(41974018);中国地震局地壳应力研究所中央级公益性科研院所基本科研业务专项资助项目(ZDJ2017-10)

Decade borehole strain observation at Guza and the precursory anomaly of the Wenchuan earthquake

QIU Ze-hua(), TANG Lei, GUO Yan-ping, ZHANG Bao-hong   

  1. Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
  • Received:2019-09-28 Revised:2020-04-23 Online:2020-08-20 Published:2020-09-02

摘要:

姑咱台的YRY-4型四元件钻孔应变仪是2006年底安装的,至今仍在正常工作,已经有十多年的分钟值观测数据.姑咱台的这种观测的高质量,首先体现在连续性上,除仪器本身的耐久性外,认真有效的运维管理是一个重要原因.这种高质量观测的另一个特点是稳定性,十年来耦合系数保持稳定,说明观测系统的稳定.这种观测数据保持了良好的自洽性,作为四元件钻孔应变观测,这是一项关键指标.所有这些指标(连续性、稳定性和自洽性),说明了观测技术和产出数据的可靠性.根据这十多年的可靠观测数据,得到两个重要认识:一个是这种仪器可以观测长期的构造应变速率,改变了过去对钻孔应变观测频响性能的认识,有助于对现今构造运动特别是地震断层现今活动性的研究;另一个是汶川地震前观测到的异常变化得到进一步确认,这为地震前兆研究提供了一个可靠的个案.不仅如此,姑咱台还进行了这种钻孔应变仪的高频观测实验,采样率达到每秒100次,与摆式地震仪相同.结果表明,这种应变仪在高频端的观测表现非常好.这为地震波研究提供了新手段.更重要的是,它说明这种钻孔应变观测是一个地球动力学的全频段观测技术.这种观测创造了一种可能性,就是将地震孕育以及发生的过程完整地记录下来:从趋势改变到蠕变,从慢地震到低频地震,从前震到主震,可以用这种四元件钻孔应变仪将所有各种变化全部记录下来.

关键词: 钻孔应变仪, 四分量钻孔应变观测, 汶川地震, 地震前兆异常, 频率响应

Abstract:

The YRY-4 type of Four-Gauge-Borehole Strainmeter (FGBS) at Guza station was deployed in late 2006 and has been working well for over one decade yielding minute sampling data. The high quality of the data is represented firstly by its continuity, which requires effective management apart from the endurability of the instrument. Secondly, another feature of the high quality of the data lies in the stability of the observation system, which can be recognised from the little variations of the coupling coefficients over these years. Thirdly, the data from the four gauges has kept good self-consistency, which is the key index for a four-gauge-borehole strainmeter. All these properties (continuity, stability and self-consistency) assure the credibility of the data as well as the instrument. We draw from the decade’s credible data two important conclusions. One is that such observation is capable of observing the long-term strain rate related to modern tectonic movements and, hopefully, it can be applied to investigations of active fault’s movements. The other is that the precursory anomaly observed before the Wenchuan earthquake is further confirmed, which supplies a solid example of case study to the earthquake precursory research. Moreover, in 2008, an observation experiment with this instrument was carried out with a sampling rate as high as 100 Hz, equivalent to that of a traditional seismograph. Results show that the borehole strainmeter behaves just as good in this high range of frequency. It has significantly enlarged the application field of this kind of instrument and, more importantly, makes it a whole-band observation in geodynamics. It suggests the possibility that we can use this single device of FGBS to record all those phenomena in the entire nucleation process of an earthquake including abrupt turning in trend, creeping, slow and low-frequency earthquakes, foreshocks and the main shock, and so on.

Key words: Borehole strainmeter, Four-Gauge-Borehole Strainmeter (FGBS), Wenchuan earthquake, Precursory anomaly of earthquake, Frequency response

中图分类号: