The Yishu fault zone （mid-segment of the Tanlu fault zone） was formed in the Presinian. Periodic tectonic activities and strong seismic events have occurred along the fault zone. During the initial stage of the Cale...The Yishu fault zone （mid-segment of the Tanlu fault zone） was formed in the Presinian. Periodic tectonic activities and strong seismic events have occurred along the fault zone. During the initial stage of the Caledonian Movement, with the proceeding of the marine transgression from the Yishu paleo-channel to the western Shandong, uneven thick sediments, composed mainly of sand, mud and carbonates of littoral, lagoon, and neritic facies, were deposited in the Yishu fault zone and western Shandong, and constructed the bottom part of the Lower Cambrian consisting of the Liguan and Zhushadong formations. Through field observations and the lab-examinations, various paleoseismic records have been discovered in the Liguan Formation and the Zhushadong Formations of the Yishu fault zone and its vicinity, including some layers with syn-sedimentary deformation structures that were triggered by strong earthquakes （i.e. seismite, seismo-olistostrome, and seismo-turbidite）. Paleoseismic records developed in the Zhushadong Formation are mainly seismites with soft-sediment deformation structures, such as liquefied diapir, small liquefied-carbonate lime-mud volcano, liquefied vein, liquefied breccia, convolute deformation （seismic fold）, graded fault, soft siliceous vein, and deformation stromatolite, as well as seismites with brittle deformation structures of semiconsolidated sediments. Paleoseismic records preserved in the Liguan Formation are not only seismo-olistostrome with a slump fold, load structure, and ball-and-pillows, but also seismo-turbidite with convolution bedding, graded bedding and wavy-bedding. However, in the western Shandong area, the closer to the Yishu fault zone, the greater the thickness of the Liguan Formation and the Zhushadong Formation, the greater the number and type of layers with paleoseismic records, and the higher the earthquake intensity reflected by associations of seismic records. This evidence indicates that tectonic taphrogenesis accompanied by strong earthquake events occurred in the Yishu fault zone during the initial stage of the Caledonian Movement, which embodied the break-up of the Sino-Korean Plate along the Paleo-Tanlu fault zone at that time.展开更多
A detailed study on geomorphic surfaces and a set of trenches on the Hohhot segment of Daqingshan piedmont fault at three sites, Kuisu, Ulan Blang, and Qingshan Grassland, revealed 7 paleoseismic events occurred along...A detailed study on geomorphic surfaces and a set of trenches on the Hohhot segment of Daqingshan piedmont fault at three sites, Kuisu, Ulan Blang, and Qingshan Grassland, revealed 7 paleoseismic events occurred along the fault segment since 19 ka BP. Those events occurred at 18.75±.75 ka, 16.97 ±.96 ka, 14.65±.67 ka, 11.82±.69 ka, 9.45±.26 ka, 6. 83±.26 ka, and 4. 50 ±0. 23 ka BP, respectively, and their average recurrence interval is 2375±432 years. From the results of constraining fault displacement and correlation between the sediments in these trenches, we found a complete paleoseismic activity history along the fault segment during this period of time.展开更多
The Tianqiaogou-Huangyangchuan fault lies east of the main peak, Lenglongling Mount, in the east part of the Qilian Mountains and is one of the major active faults on the eastern section of the Qilian Mountains. The f...The Tianqiaogou-Huangyangchuan fault lies east of the main peak, Lenglongling Mount, in the east part of the Qilian Mountains and is one of the major active faults on the eastern section of the Qilian Mountains. The fault is separated into two segments at Guanjiatai village, the eastern and western segments, and has undergone obvious movement since the Holocene. Six trenches were excavated to study the pa!eoseismic activity along the fault. Integrated and comparative analysis of sediments in the trenches reveals 7 paleoseismic events and a historic earthquake on the fault since the Holocene. Their ages are： event Ⅰ is （10743 ± 343 ）a BP,event Ⅱ （9038 ± 39）a BP, event Ⅲ （7050 ± 577）a BP, event Ⅳ （4847 ± 185）a BP, event Ⅴ（3562 ± 190）a BP, event Ⅵ （2476 ±194） a BP, and event Ⅶ（1505 ± 253）, respectively, and event Ⅷ is the 1927 Gulang Ms8. 0 earthquake. It indicates that the fault might have contributed to the 1927 Gulang Ms8.0 earthquake. The temporal and spatial distribution of the paleoseismic events is relatively uniform and is characterized approximately by a quasiperiodic recurrence.展开更多
There are many different processes generating soft-sediment deformation. This paper is confined to deformations generated by paleoseismic events in Sweden. The Paleoseismic Catalogue of Sweden includes 66 events. The ...There are many different processes generating soft-sediment deformation. This paper is confined to deformations generated by paleoseismic events in Sweden. The Paleoseismic Catalogue of Sweden includes 66 events. The structural characteristics and driving forces of liquefaction are discussed in details. “Crypto-deformations” refer to a special type of fluidization not affecting the sedimentary bedding itself, but the internal orientation of the ChRM and AMS carrying particles. Extensive turbidites are formed at some events. They constitute useful “marker-varves”. Out of the 66 paleoseismic events, 31 are dated by varves as to a single year (in one case even to the season of a year). Tsunamites are recorded from 19 of the paleoseismic events;some with wave-heights up to 15 - 20 m.展开更多
The Swedish catalogue of paleoseismic events includes 64 separate events. The seismic activity was especially high, in magnitude and frequency, in the Late Glacial with peak rates of glacial isostatic uplift. At about...The Swedish catalogue of paleoseismic events includes 64 separate events. The seismic activity was especially high, in magnitude and frequency, in the Late Glacial with peak rates of glacial isostatic uplift. At about 12,400 C14-years BP (14,600 cal?yrs BP), there was a very strong event on the Swedish west coast. The magnitude was estimated at M > 8. It was linked to intensive liquefaction and a major tsunami event. In this paper we describe sedimentological structures of liquefaction, ground shaking and tsunami wave actions from the Hunnestad gravel pits, to the east of the city of Varberg on the Swedish West Coast. The liquefaction structures documented offer impressive and educational insight into the process of liquefaction at high-magnitude earthquakes.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.:41272066)the Scientific Research Key Project of Shandong Province’s Geoscience Forum(LDXHLT-2007-10-001)the China Geological Survey Project(Grant No.:1212010510509)
文摘The Yishu fault zone （mid-segment of the Tanlu fault zone） was formed in the Presinian. Periodic tectonic activities and strong seismic events have occurred along the fault zone. During the initial stage of the Caledonian Movement, with the proceeding of the marine transgression from the Yishu paleo-channel to the western Shandong, uneven thick sediments, composed mainly of sand, mud and carbonates of littoral, lagoon, and neritic facies, were deposited in the Yishu fault zone and western Shandong, and constructed the bottom part of the Lower Cambrian consisting of the Liguan and Zhushadong formations. Through field observations and the lab-examinations, various paleoseismic records have been discovered in the Liguan Formation and the Zhushadong Formations of the Yishu fault zone and its vicinity, including some layers with syn-sedimentary deformation structures that were triggered by strong earthquakes （i.e. seismite, seismo-olistostrome, and seismo-turbidite）. Paleoseismic records developed in the Zhushadong Formation are mainly seismites with soft-sediment deformation structures, such as liquefied diapir, small liquefied-carbonate lime-mud volcano, liquefied vein, liquefied breccia, convolute deformation （seismic fold）, graded fault, soft siliceous vein, and deformation stromatolite, as well as seismites with brittle deformation structures of semiconsolidated sediments. Paleoseismic records preserved in the Liguan Formation are not only seismo-olistostrome with a slump fold, load structure, and ball-and-pillows, but also seismo-turbidite with convolution bedding, graded bedding and wavy-bedding. However, in the western Shandong area, the closer to the Yishu fault zone, the greater the thickness of the Liguan Formation and the Zhushadong Formation, the greater the number and type of layers with paleoseismic records, and the higher the earthquake intensity reflected by associations of seismic records. This evidence indicates that tectonic taphrogenesis accompanied by strong earthquake events occurred in the Yishu fault zone during the initial stage of the Caledonian Movement, which embodied the break-up of the Sino-Korean Plate along the Paleo-Tanlu fault zone at that time.
基金The research as one of the key project was supported by Joint Seismological Science Foundation grant 95-07-421. Contribution No. 2001 B001, Institute of Geology, China Seismological Bureau, China.
文摘A detailed study on geomorphic surfaces and a set of trenches on the Hohhot segment of Daqingshan piedmont fault at three sites, Kuisu, Ulan Blang, and Qingshan Grassland, revealed 7 paleoseismic events occurred along the fault segment since 19 ka BP. Those events occurred at 18.75±.75 ka, 16.97 ±.96 ka, 14.65±.67 ka, 11.82±.69 ka, 9.45±.26 ka, 6. 83±.26 ka, and 4. 50 ±0. 23 ka BP, respectively, and their average recurrence interval is 2375±432 years. From the results of constraining fault displacement and correlation between the sediments in these trenches, we found a complete paleoseismic activity history along the fault segment during this period of time.
文摘The Tianqiaogou-Huangyangchuan fault lies east of the main peak, Lenglongling Mount, in the east part of the Qilian Mountains and is one of the major active faults on the eastern section of the Qilian Mountains. The fault is separated into two segments at Guanjiatai village, the eastern and western segments, and has undergone obvious movement since the Holocene. Six trenches were excavated to study the pa!eoseismic activity along the fault. Integrated and comparative analysis of sediments in the trenches reveals 7 paleoseismic events and a historic earthquake on the fault since the Holocene. Their ages are： event Ⅰ is （10743 ± 343 ）a BP,event Ⅱ （9038 ± 39）a BP, event Ⅲ （7050 ± 577）a BP, event Ⅳ （4847 ± 185）a BP, event Ⅴ（3562 ± 190）a BP, event Ⅵ （2476 ±194） a BP, and event Ⅶ（1505 ± 253）, respectively, and event Ⅷ is the 1927 Gulang Ms8. 0 earthquake. It indicates that the fault might have contributed to the 1927 Gulang Ms8.0 earthquake. The temporal and spatial distribution of the paleoseismic events is relatively uniform and is characterized approximately by a quasiperiodic recurrence.
文摘There are many different processes generating soft-sediment deformation. This paper is confined to deformations generated by paleoseismic events in Sweden. The Paleoseismic Catalogue of Sweden includes 66 events. The structural characteristics and driving forces of liquefaction are discussed in details. “Crypto-deformations” refer to a special type of fluidization not affecting the sedimentary bedding itself, but the internal orientation of the ChRM and AMS carrying particles. Extensive turbidites are formed at some events. They constitute useful “marker-varves”. Out of the 66 paleoseismic events, 31 are dated by varves as to a single year (in one case even to the season of a year). Tsunamites are recorded from 19 of the paleoseismic events;some with wave-heights up to 15 - 20 m.
文摘The Swedish catalogue of paleoseismic events includes 64 separate events. The seismic activity was especially high, in magnitude and frequency, in the Late Glacial with peak rates of glacial isostatic uplift. At about 12,400 C14-years BP (14,600 cal?yrs BP), there was a very strong event on the Swedish west coast. The magnitude was estimated at M > 8. It was linked to intensive liquefaction and a major tsunami event. In this paper we describe sedimentological structures of liquefaction, ground shaking and tsunami wave actions from the Hunnestad gravel pits, to the east of the city of Varberg on the Swedish West Coast. The liquefaction structures documented offer impressive and educational insight into the process of liquefaction at high-magnitude earthquakes.
