A 125 Kyr‐long geological record of seismic source repeatability: the Messina Straits (southern Italy) and the 1908 earthquake (Ms 71/2)
A 125 Kyr‐long geological record of seismic source repeatability: the Messina Straits (southern Italy) and the 1908 earthquake (Ms 71/2)
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125 凯尔长的震源重复性地质记录：墨西拿海峡（意大利南部）和 1908 年地震（Ms 71/2）
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
D. Pantosti
中科院分区：
文献类型：
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作者：
G. Valensise;D. Pantosti
早在本世纪初，人们就描述了沿着主要活动带的分段发生的特征地震。1908年发生在梅西纳海峡的盲目正断层大地震为研究特征地震的重复性和断裂带主要特征在100Kyr量级上的持续性提供了机会。我们将1908年破裂过程的地震学和大地测量学描述与由海洋阶地、海洋沉积单元和地貌特征在不同地层水平记录的长期地壳形变进行了比较。受大的正断层地震影响的地区及其周围丰富的海岸隆起特征表明，同震应变叠加在区域尺度上更快的隆起上。我们详细研究了125凯尔历史最低的紧急阶地的形变模式，发现它模拟了地震后观察到的海拔变化模式。这表明：(1)1908年的地震是特有的；(2)在过去的125Kyr中，地震段的边界是静止的；(3)即使是最大同震释放区的位置也不会在多次地震循环中发生变化。根据125Kyr阶地的观测高度与1908年位移的比较，我们估计1908年地震的平均重复时间为1000±年。我们还研究了老阶地的高度、位置、年龄和变形状态，发现(1)该地区的隆升开始于1 Ma左右，此后一直相当均匀地持续到0.9-1.4 mm yr-1；(2)在此期间海峡以10-20 mm yr-1的速度缩小；(3)梅西纳海峡的所有主要地貌特征都是区域快速隆升、1908型同震沉降和全球海平面波动共同作用的结果。
The occurrence of characteristic earthquakes along segments of major active belts has been described as early as the beginning of the century. The large 1908, Messina Straits, blind normal faulting earthquake provides an opportunity to investigate the repetition of characteristic earthquakes and the persistency of the main features of the fault zone over a time-scale in the order of 100 Kyr. We have compared seismological and geodetic descriptions of the 1908 rupture process with long-term crustal deformation recorded at different stratigraphic levels by marine terraces, marine sedimentary units, and landscape features. The wealth of elevated coastal features in and around a region affected by large normal faulting earthquakes indicates that coseismic strain is superimposed on much faster uplift on a regional scale. We investigated in detail the pattern of deformation of the 125 Kyr-old, lowest emergent terrace, and found that it mimics the pattern of elevation changes observed following the earthquake. This suggests (1) that the 1908 earthquake is characteristic, (2) that its segment boundaries have been stationary during the past 125 Kyr, and (3) that even the locations of the regions of largest coseismic release do not change through many seismic cycles. Based on a comparison between observed heights of the 125 Kyr terrace and 1908 displacements, we estimated an average repeat time of 1000± yr for a 1908-type earthquake. We also investigated the height, position, age and state of deformation of older terraces, and found (1) that uplift of the region started about 1 Ma and has since continued rather uniformly at 0.9–1.4 mm yr-1, (2) that during this time the Straits have narrowed at a rate of 10–20 mm yr-1, and (3) that all the main geomorphic features of the Messina Straits result from the interaction of fast regional uplift, 1908-type coseismic subsidence, and global sea-level fluctuations.