欢迎访问《高校地质学报》官方网站,今天是
分享到:

J4

• 文章目录 • 上一篇    下一篇

1995年日本兵库县南部地震时淡路岛上出现的地震断层的形态特征

林爱明   

  1. 东京大学地震研究所
  • 收稿日期:1995-03-20 修回日期:1995-03-20 出版日期:1995-09-20 发布日期:1995-09-20

MORPHOLOGICAL CHARACTERISTICS OF THE EARTHQUAKE SURFACE RUPTURES ON AWAJI ISLAND , ASSOCIATED WITH THE 1995 SOUTHERN HYOGO PREFECTURE EARTHQUAKE

Aiming Lin   

  1. Earthquake Research Institute, The University of Tokyo, Yayol 1-1, Bunkyo-ku, Tokyo 113, Japan
  • Received:1995-03-20 Revised:1995-03-20 Online:1995-09-20 Published:1995-09-20

摘要: 1995年日本兵库县南部地震时在淡路岛上出现的地表地震断层主要由三条地表破裂带组成、野岛地震断层、松帆地震层和楠本地震断层。野岛地震断层从淡路岛北端的淡路町住西南延伸到一宫町的尾崎,长达18km,其北段沿着早期存在的野岛断层分布,而南段则作为新断层出现,野岛地震断层的断层的北段主要由一些相互平行或次平行的右列剪切断层和许多左列和性裂隙组成,其南段则是由集中在十多米宽的大量不连续的地表破裂带所组成。野岛地震断层一般走向N30°~60°E倾向SE,地貌错位和断层擦痕均显示出此断层为一具有逆断层性质的右旋走滑断层,沿一些主要露头测定的北段水平位移量一般为100~200cm,垂直位移量为5O~100cm;而南段的水平、垂直位移量均只有几厘米至20cm。最大位移量在平林断层崖测得;水平180cm、垂直l30cm、实际位移量2l5cm。松帆地震断层走向N40°~60°W,沿着淡路岛北端部的海岸线分布,长达约1km。楠本地震断层沿早期存在的楠本断层出现,分布于淡路岛东北部的海岸边上,走向N35°~6O°W倾向NW 。根据地表地震断层的形态及地貌错位特征,野岛地震断层可被分为四条断层段,并在形态上呈现右列。地质和地貌证据以及余震分布的特征清楚地表明这4条断层段的几何形态和分布特征是受早期存在的地质构造所控制的,同时也说明了地震断层的破裂过程具有拉分(pulling-apart)和推隆(pushing-up)的过程,这两个过程分别产生了张性裂隙、拉分盆地、逆断层和挤压隆起等构造。

Abstract: The earthquake fault system on northern Awaji island accompanying the 1995 Southern Hyogo Prefecture Earthquake consists of three earthquake surface rupture zones, namely Nojima Earthquake Fault, Matsuho Earthquake Fault, an d Kusumoto Earthquake Fault. The Nojima Earthquake Fault,18 km in length, extends from Awaji-cho and the northern tip of Awaji island to Ichinomiya-cho and wag developed along the pre-existing Nojlma fault in the northern segment and as a new fault in the southern segment. The northern segment of the Nojima Earthquake Fault is composed of several subparallel shear faults showing a right-step enechelon form and a lot of extensional cracks showing a left-step enechelon form, whereas the southern segment consists of some discontinuous surface ruptures which are concentrated in a narrow zone a few tens of meters in width. This fault shows a general trend striking N 30°-60°E, 75°-85° dipping to SE. The deformational topography and striations on the the fault plane generated during earthquake faulting show that the Nojima Earthquake Fault is a right-lataral strike-slip fault with minor reverse movement. Displacements measured at a lot of outcrops are generally 1.0-2.0 m in horizontal direction and 0.5-1.0 m in vertical directions in the northern segment and a few cm to 20 cm in both horizontal and vertical direction in the southern segment. The largest displacements are 180 cm in horizontal direction,130 cm in vertical direction, and 215 cm in netslip measured at the Hirabayashi fault scarp. The Matsuho Earthquake Fault striking N 40°-60°W is also found along the coastal line trending NW -SE at Awaji-cho for about 1 km at the north end of Awaji island. The Matsuho Earthquake Fault extends along the pre-existing geological Kusumoto fault for about l km near the noutheastern coastal line, generally striking N 35°一60°E and 60°-70°dipping to NW. Based upon morphological and geomorpholocal characteristics,the Nojima Earthquake Fault can be divided into four fault segments which exhibit a right-step enechelon form. Geological and geomorphological evidence and aftershock epicenter distributions show clearly that the distributions an d geometry of these four segments are controlled by the pre-existing geological structures. It documented that deformation along the earthquake faults involves the pulling-apart and the pushing-up processes which have produced the extensional cracks, pull—apart basins, flexural folds and pressure ridges.