Recurrence Time of Large Events on Active Faults in Korea

韩国活断层重大事件重现时间

• 批准号: 06041060
• 负责人: OIKE Kazuo
• 金额: $ 2.94万
• 依托单位: Kyoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 无数据
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06041060/
• 关键词: Active fault; Yangsan fault; Ulsan fault; Fault topography; Trench excavation survey; Crustal movement; Large earthquake; Recurrence time

The yangsan fault in the southeastern part of Korea trends about 200km with ca NNE-SSW direction and accompanies the wide shattered zone. The active fault topography and geology have investigated along this fault system and trench excavation had been carried out across this fault. It is confirmed that this fault cleary dislocates the river terrace surfaces and their deposits with the predominantly right-lateral com-ponent of vertical displacement upthrown to the east (Okada and others, 1994).The large-scale construction for making a new town has now been conducted at the southern part of Eonyang, Ulsan County, where many trench excavation surveys have carried out to clarify the associated crustal deformation along the main fault and subordinary faults. The following results have been gotten from these investigations ; The high terrace at south of Eonyang, which has been formed by the former river flowed to the northeastward, had originally declined to northeast, but is now tilting to w … More est in the reverse direction. The gravels forming the high terrace has been deformed by the flexure movement. The vertical amount of displacement on the high terrace reaches about 5 meters. Although several faults are recognized within the trench walls, these rupturing did not extend to the surface.The Ulsan fault system extends about 40km with N-S or NNW to SSE direction. The surface trace is remarkably sinous. The Ulsan fault is a typical reverse fault, considering from the expression on the outcrop and the style of surface deformation. As geomorphic surfaces and deposits formed during late Quatenary time are clearly dislocated, Ulsan fault is really active one. The vertical amount of displacement along this fault is 5m on the middle terrace, and 15m on the high terrace. These values indicate the cumulative offsetting in the late Quatenary.The outcrops showing active fault were clearly observed at two localities. The shattered granite thrust over the gravel layrs with the strike of N-S direction and the dip of 25-30ﾟ E on north wall of Sagok reservoir at east of Malbang-ri settlement ; detailed structures were sketched after cleaning of this wall. Well shatterd granite is overridden on the slightly weathered gravel layrs on the river (Yeonan Stream) -side outcrop of at the northeastern part of Kaegok-ri settlement.The silty sediments consisting of the upper part of the middle terrace at Malbang-ri were clearly disturbed by liquefaction. This phenomena indicate the occurrence of large earthquakes in this area. Recurrence time of large events in the southeast-ern part of Korea will be treated after getting the ages of the terrace surfaces and its deposits.As the marine Miocene sediments are well distributed around Pohan basin, geological surveys have been carried out to clarify post-Miocene movements of the Yansang fault. The detailed analyzes of micro-fossils and molluscas have been investigated in the laboratory works. Less

位于朝鲜东南部的阳山断裂沿约NNE-SSW方向延伸约200公里，并伴随着宽阔的破碎带。对该断裂系统的活动断裂地貌和地质进行了调查，并在该断裂上进行了沟槽开挖。已证实该断裂使河流阶地及其沉积错位，向东以右旋垂直位移为主(Okada等人，1994)。蔚山县鄂阳南部现已进行了大规模的新城建设，并进行了多次沟槽开挖测量，以弄清与之相关的沿主干断裂和次普通断裂的地壳形变。研究结果表明：鄂阳南部的高阶地是由原流向东北方向的河流形成的，原本向东北倾斜，现在向西倾斜(w…)。更多的是在相反的方向上。形成高阶地的砾石因挠曲运动而变形。高台上的垂直位移量达到5米左右。尽管在槽壁内发现了几条断裂，但这些断裂并没有延伸到地表。蔚山断裂系统沿N-S或NNW向SSE方向延伸约40公里。表面的痕迹是非常弯曲的。蔚山断裂是一条典型的逆断层，从露头表现形式和地表变形方式来看，蔚山断裂是一条典型的逆断层。由于晚四纪形成的地貌面和沉积明显错动，蔚山断裂才是真正的活断层。沿该断层的垂直位移量在中阶地上为5m，在高阶地上为15m。这些值指示了第四纪晚期的累积错动。在两个地点清楚地观察到露头显示了活动断层。破碎的花岗岩冲出碎石层，走向为N-S方向，倾角为25-30ﾟE，位于马尔邦-里定居点以东的萨戈克水库北侧，清洗后绘制了详细的结构图。在Kaegok-ri定居点东北部，河流(延南溪)一侧露头的微风化砾石层上覆盖了破碎的花岗岩，Malbang-ri中间阶地上部的粉质沉积物明显受到液化干扰。这一现象表明该地区曾发生过大地震。韩国东南部大地震的复发时间将在获得阶地表面及其沉积的年龄后进行处理。由于坡汉盆地周围分布着较好的海相中新世沉积物，因此开展了地质调查，以弄清岩桑断裂的后中新世活动。实验室对微体化石和软体动物进行了详细的分析。较少

项目成果

OKADA,A: "Active fault topography and trench S'urvey in the Central Part of the Yangsan fault, Southeast Korea" Journal of Geography. 103. 111-126 (1994)

OKADA，A：“韩国东南部梁山断层中部的活动断层地形和海沟测量”地理学杂志。

WATANABE,M.: "Trench survey of the Yangsan fault at Oenyang, Southeast korea, 1994." Active fault research. (in preparation).

WATANABE,M.：“韩国东南部 Oenyang 梁山断层的海沟勘察，1994 年。”

岡田篤正: "梁山断層(韓国東南部)中央部の活断層地形とトレンチ調査" 地学雑誌. 103. 111-126 (1994)

Atsumasa Okada：“梁山断层中部的活动断层地形和沟渠调查（韩国南部）”地质杂志 103. 111-126 (1994)。

岡田篤正: "蔚山断層系(韓国東南部)中央部の活断層地形と断層露頭" 地学雑誌. (発表予定).

Atsumasa Okada：“蔚山断层系统中部的活动断层地形和断层露头（韩国南部）”地质杂志（待出版）。

渡辺満久: "1994年度梁山断層トレンチ調査(彦陽地区)" 活断層研究. (発表予定).

渡边光久：《1994年凉山断层沟调查（彦阳地区）》活动断层研究（报告预定）。