地震重复间隔及震时位移与无震位移比值的实验研究

EXPERIMENTAL STUDY OF RECURRENCE INTERVAL AND THE RATIO OF CO-SEISMIC TO ASEISMIC DISPLACEMENT

了解地区地震重复间隔对地震区划与地震预报均十分重要。鉴于在自然条件下研究地震重复间隔的艰巨性,本文利用实验方法探讨影响粘滑事件重复时间间隔的因素。实验表明,粘滑事件在一定条件下具有准周期性。岩性、围压和应变速率不同,事件的周期不同。高围压下周期长。应变速率对粘滑事件周期的影响较复杂,在100MPa围压下,位移速率变化,每次事件的位移量不变。在300 MPa围压下,由于位移速率减慢,每次事件的位移量增大。 定义一个事件过程中震时位移量和无震位移量之和为全过程总位移量,并且定义α为震时位移量与总位移量之比值。实验表明,每次粘滑事件中存在无震位移量。微密岩石的α值比疏松岩石的大;同种岩石高围压下α值比低围压下小;断面上随着粘滑次数增多,α值变大。α值的变化范围为0.1—0.5。

It is important for earthquake zoning and prediction to know the earthquake recurrence interval m a region. In view of the arduousness for studying the earthquake recurrence interval in the field, this paper probes into the factors affecting the recurrence interval of stick-slip, events by using experimental method. The experiments show that stick-slip events are of quasi-ptriodicity in a certain condition. The periodicity of events are different for different Iithology, confining pressure and strain rate used in the experiments. The period is long under high pressure. The influence of strain rate on the period of stick-slip event is relatively complex. Under 100 MPa confining pressure, the displacement rate changes while the displacement of each event does not change. Under the 300 MPa confining pressure, as the displacement rate decreases, the displacement of each event increases.The sum of coseismic displacement and aseismic displacement in a process of an event is defined as the total displacement amount in the whole process, and a is defined as the ratio of co-seismic displacement to the total displacement. The experiments show that there exists aseismic displacement amount in every stick-slip process. The a value of compact rocks is greater than that of loose rocks; the a value for same rock is smaller under high confining pressure than that under low confining pressure; on a fault plane the a value increases with the increase of the number of stick-slip events. The variation range of a value is 0.1-0.5.