Surface deformation and geologic structures associated with active blind faults

与活动盲断层相关的地表变形和地质结构

• 批准号: 15300300
• 负责人: IKEDA Yasutaka
• 金额: $ 10.43万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-15300300/
• 关键词: active fault; blind fault; reflection seismic profiling; tectonic geomorphology; gravity survey; 地震; 地下構造

We performed seismic reflection profiling and gravity profiling across selected active faults in northeast and central Japan, in order to clarify the mechanism of surface deformation and geologic structures associated with blind active faulting. The following results were obtained :1.Most of presently active faults in northeast Japan were originated from Miocene normal faults, and have been reactivated as thrust faults under compressive stress regime since Pliocene time. Seismic reflection and gravity surveys were performed across the source area of the 2003 Northern Miyagi earthquake of Mw 6.4. We found Miocene geologic structures indicative of a large amount of normal slip on the source fault, although focal mechanism solutions of the earthquake are of thrust type.2.The source region of the 2004 Chuetsu earthquakes is located in a fold-and-thrust belt. Surface and subsurface geologic data suggest that this fold-and-thrust belt is underlain by a large-scale detachment fault, which was responsible for the stretching (rifting) of, and the deposition of thick sediments in, this area in Miocene time. Most of aftershocks occurred below the detachment horizon. Therefore it is likely that the source faults of the 2004 earthquakes were not related to the thin-skinned structure but represent internal deformation of Mesozoic-Paleozoic basement beneath the detachment.3.In contrast to northeast Japan, inversion tectonics is not obvious in central Japan. It has been believed that the Ina Valley fault zone was newly born in early Quaternary time. Our seismic reflection and gravity survey, however, revealed that a blind active thrust fault exists beneath basin-fill sediments in the Ina Valley. On the hanging-wall side of this blind fault is a thick pile of sedimentary rocks, indicating normal slip on this fault possibly in Miocene time. This suggests that crustal structures of southwest Japan also have been affected by Miocene extension.

我们在日本东北部和中部选定的活动断裂上进行了地震反射剖面图和重力剖面图，以阐明与盲目活动断裂有关的地表变形和地质构造的机制。结果表明：1.日本东北部现今的活动断裂大多起源于中新世正断层，自上新世以来在挤压应力状态下又被重新激活为逆冲断裂。在2003年宫城北部6.4级地震的震源区进行了地震反射和重力测量。我们发现了中新世地质构造，表明震源断层上有大量的正滑动，尽管地震的震源机制解是逆冲型的。2.2004年楚楚地震的震源区位于褶皱冲断带上。地表和地下地质资料表明，该褶皱冲断带被一条大规模的滑脱断层所覆盖，该断层在中新世时期负责该地区的伸展(裂谷)和厚沉积物的沉积。大部分余震发生在滑脱地平线以下。因此，2004年地震的震源断层很可能与薄皮构造无关，而是拆离之下中、古生代基底的内部变形。3.与日本东北部相比，日本中部的反转构造不明显。人们认为，伊纳谷断裂带是第四纪早期新生的。然而，我们的地震反射和重力调查显示，在伊纳河谷的盆地充填沉积之下存在一条盲目活动的逆冲断层。在这条隐伏断裂的上盘一侧有一堆厚厚的沉积岩，这表明该断裂可能在中新世发生了正常滑动。这表明日本西南部的地壳结构也受到了中新世伸展的影响。

项目成果

Ogaki Quadrangle, Active Fault Map in Urban Area 1 : 25000

大垣四边形，市区1号活动断层图：25000

• 发表时间: 2005
• 期刊: Technical Report (Geographical Survey Institute of Japan) D1-No.449
• 作者: Suzki;Y.;et al.
• 通讯作者: et al.

Dazaifu Quadrangle, Active Fault Map in Urban Area 1 : 25000

太宰府四合院，市区1号活动断层图：25000

• 发表时间: 2004
• 期刊: Technical Report (Geographical Survey Institute of Japan) D1-No.435
• 作者: Ikeda;Y.;et al.
• 通讯作者: et al.

今泉 俊文: "都市圏活断層図 1:25,000「泊」, 国土地理院技術資料 D.1-No.416"国土地理院. 1 (2003)

Toshifumi Imaizumi：“城市地区活动断层图1：25,000“泊”，日本地理空间信息管理局技术数据D.1-No.416”日本地理空间信息管理局1（2003）。

Seismological and geological characterization of the crust in the southern part of northern Fossa Magna, central Japan

日本中部大窝北部南部地壳的地震学和地质特征

• 发表时间: 2004
• 期刊: Earth Planets Space 56
• 作者: Sato;H.;Iwasaki;t.;Ikeda;Y.;Takeda;T.;Matsuta;N.;Imai;T.;Kurashimo;E.;Hirata;N.;SiSakai;S.;Elouai;D.;Kawanaka;N.;Kawasaki;S.;Abe;S.;Kozawa;T.;Ikawa;T.;Arai;Y.;Kato;N.
• 通讯作者: N.

Active faults and folds in and around the source region of the Chuetsu earthquake of 2004

2004年中越地震震源区及其周边的活动断层和褶皱

• 发表时间: 2006
• 期刊: Chikyu, Spec. Issue 53
• 作者: Ikeda;Y.
• 通讯作者: Y.