倾斜异常图象分类及其特征浅析

PRELIMINARY OPINION ON THE FEATURES AND CLASSIFICATION OF ANOMALY PATTERNS OF CRUSTAL TILT

  • 摘要: 本文搜集与整理了我国几十次大、中强地震,震前、震时的地倾斜异常图象,按其形态大致可分为五类:Ⅰ.震前倾斜记录曲线渐变——回复——发震(多见于远震);Ⅱ.震前倾斜记录曲线突变(阶跃)——发震(多见于近震);Ⅲ.震前倾斜记录曲线扰动或单向脉冲——正常——发震;Ⅳ.震前倾斜潮汐记录曲线畸变——发震;Ⅴ.震前倾斜记录曲线脉动(曲线加粗)——发震,其特征为:1.异常形态呈多样性;2.异常出现在震前几分钟到几十小时;3.异常幅值一般在几毫秒至十分之几角秒(10-8——10-6rad),个别达几角秒(10-5rad);4.异常倾斜方向多半与震中方位有关;5.异常有由远及近、从外到内(震中)的迁移现象。文章作者还结合模拟实验和地震模式,讨论了地震前倾斜异常的有关问题。

     

    Abstract: Ill this paper, the anomaly patterns of ground tilt before and during dozens of large and moderately strong earthquakes of China had been gethered and studied. They can be divided into five kinds as follows:1. The recorded tilt curves show a gradual change before the earthquake and then return to normal before the occurrence of the earthquake, such sequences are ofter seen at stations far from the epicentre;2. The recorded curves show sudden changes (step changes) before the occurrence of earthquakes, such changes are often ,seen at stations near the epicentre;3. The recorded tilt curves show a series, of disturbance (or one-way pulses) before the earthquake and become nomal until the occurrence of the earthquake;4. The recorded curves of tilt tide show distortion until the occurrence of the earthquake;5. The recorded tilt curves display a series of small tremors so that the recorded trace becomes thicker until the earthquake occurs.The fundamental features of the records are as follows: (1) The anomaly patterns show variety; (2) The anomalies occur from a few minutes to tens of hours before the earthquakes; (3) The amplitude of anomalies is of the order of 10-8-10-7, a few amounting to 10-6, or even to 10-5; (4) The direction of anomalous tilt is often related to the azimuth of the epicenter of the earthquake with respect to the station; (5) When an anomaly due to the same earthquake is recorded by many stations, the anomaly is first detectable at stations far removed from the epicentre and then at the stations nearer to the epicenter.Finally, in this paper some problems concerned with tilt anomaly before earthquakes results of rock sample experiments and seismic models are discussed.

     

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