试论截直断裂与地震——以华北的3条北东向断裂为例
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摘要
截直断裂是发育在大型的走滑或斜滑断裂带末端的分支断裂。断裂带长期反复活动,在其末端,因地壳应力消散或减弱,断裂走向发生急剧转折之后,在转折点附近产生了截直断裂。截直断裂的性状可以归纳为如下几点:(1)发育于接近主干断裂末端的转折点附近,其走向与主干断裂的总体走向一致,性状与主干断裂相似;(2)切割的地层或控制的沉积较主干断裂为新;(3)断裂的长度较小,断面较主干断裂为陡;(4)形成的时代为主干断裂发育的后期或新于主干断裂;(5)是活动断裂带中更为活跃的段落,有较强的“生命力”。 截直断裂循着主干断裂既定的走向方向滑动,当向前延展时,如在前方遇到横亘其前的构造障碍,可能发生强震,否则只发生中小地震。
Made-straight faults are the secondary faults which developed at the ends of great strike-slip or oblique fault zones. After a slip fault developed for a long time, the stress at its ends died out and the strike of the fault changed rapidly, as a result the made-straight faults developed near the turning points. The Characteristics of the made-straight faults can be summerized up as follows:
1. They develop near the turning points closely to the ends of main faults ,go along the strike of the main faults. Their character are similar.
2. The strata cut by made-straight faults and sediment controled by them arc younger than that by the main faults.
3. They are shorter and steeper than the main faults.
4. They developed in or after the later stage of the main faults. 5. They are the more active sections of the faults.
Slipping along the stike of the main faults. the made-straight faults cause great earthquakes if they are obstructed by other structures in front, otherwise cause moderate or small earthquakes.
Made-straight faults are the secondary faults which developed at the ends of great strike-slip or oblique fault zones. After a slip fault developed for a long time, the stress at its ends died out and the strike of the fault changed rapidly, as a result the made-straight faults developed near the turning points. The Characteristics of the made-straight faults can be summerized up as follows:
1. They develop near the turning points closely to the ends of main faults ,go along the strike of the main faults. Their character are similar.
2. The strata cut by made-straight faults and sediment controled by them arc younger than that by the main faults.
3. They are shorter and steeper than the main faults.
4. They developed in or after the later stage of the main faults. 5. They are the more active sections of the faults.
Slipping along the stike of the main faults. the made-straight faults cause great earthquakes if they are obstructed by other structures in front, otherwise cause moderate or small earthquakes.
引文
江娃利等,1993,山西交城断裂全新世活动证据及第四纪活动历史,地质构造与地壳应力文集,No.6,98-104。
刘巍等,1994,太原盆地的应力场特征,山西地震,No,1,18 24。
孟宪梁等,1983,1679年三河-平谷大震的地震断裂带,地震,No.3,18 23。
彭一民等,1981,北京平原区同生断裂的某些特征及其研究意义,地震地质,Vol.3,No.2,57-64。
杨承先,1984,沧东断裂带的地质特征与地震活动性,地震科学研究,No.4,49-52。
杨承先,1995,太原盆地构造格局与地震活动水平的新认识,华北地质矿产研究,Vol.2,No.3。
刘巍等,1994,太原盆地的应力场特征,山西地震,No,1,18 24。
孟宪梁等,1983,1679年三河-平谷大震的地震断裂带,地震,No.3,18 23。
彭一民等,1981,北京平原区同生断裂的某些特征及其研究意义,地震地质,Vol.3,No.2,57-64。
杨承先,1984,沧东断裂带的地质特征与地震活动性,地震科学研究,No.4,49-52。
杨承先,1995,太原盆地构造格局与地震活动水平的新认识,华北地质矿产研究,Vol.2,No.3。
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