Prehistoric earthquake history revealed by lacustrine slump deposits
Prehistoric earthquake history revealed by lacustrine slump deposits
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湖泊塌陷沉积物揭示的史前地震历史
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
S. Ward
中科院分区：
文献类型：
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作者：
M. Schnellmann;F. Anselmetti;D. Giardini;J. Mckenzie;S. Ward
在过去的15K.Y中，记录到了5次强烈的古地震事件。在瑞士中部卢塞恩湖地下的一系列塌陷沉积中，首次揭示了中欧地震最活跃地区之一的古地震历史。尽管海洋和湖泊环境中的许多塌陷沉积以前被归因于历史地震，但缺乏详细的三维地层对比，结合准确的年代测定，阻碍了将多个塌陷沉积用作古地震指示。这项研究调查了描述良好的公元1601年地震(I=VII-VIII，Mw∼6.2)在卢塞恩湖沉积物中的指纹。这场地震在湖的不同次盆地内引发了许多同步的崩塌和巨型重叠岩，产生了一种特征模式，可以用来为史前崩塌事件指定地震触发机制。对于每个地震事件层，通过准三维高分辨率地震勘探网格，通过单个滑塌沉积之间的地震地层对比来建立滑塌同步性。四个史前事件分别发生在2420、9770、13,910和14,560年前，通过加速器质谱仪、~(14)C测量和年代学确定一系列长重力岩芯的年代。这些复发时间是评估该地区地震危险性的基本因素。滑坡引发的海啸和地震波还放大了湖滨社区的地震风险。对这种海啸波的数值模拟显示，波高达3米，表明湖泊环境中存在海啸风险。
Five strong paleoseismic events were recorded in the past 15 k.y. in a series of slump deposits in the subsurface of Lake Lucerne, central Switzerland, revealing for the first time the paleoseismic history of one of the most seismically active areas in central Europe. Although many slump deposits in marine and lacustrine environments were previously attributed to historic earthquakes, the lack of detailed three-dimensional stratigraphic correlation in combination with accurate dating hampered the use of multiple slump deposits as paleoseismic indicators. This study investigated the fingerprint of the well-described A.D. 1601 earthquake (I = VII–VIII, Mw ∼ 6.2) in the sediments of Lake Lucerne. The earthquake triggered numerous synchronous slumps and megaturbidites within different subbasins of the lake, producing a characteristic pattern that can be used to assign a seismic triggering mechanism to prehistoric slump events. For each seismic event horizon, the slump synchronicity was established by seismic-stratigraphic correlation between individual slump deposits through a quasi-three-dimensional high-resolution seismic survey grid. Four prehistoric events, dated by accelerator mass spectrometry, 14C measurements, and tephrochronology on a series of long gravity cores, occurred at 2420, 9770, 13,910, and 14,560 calendar yr ago. These recurrence times are essential factors for assessing seismic hazard in the area. The seismic hazard for lakeshore communities is additionally amplified by slump-induced tsunami and seiche waves. Numerical modeling of such tsunami waves revealed wave heights to 3 m, indicating tsunami risk in lacustrine environments.