Seismic moment summation for historical earthquakes in Italy: Tectonic implications
Seismic moment summation for historical earthquakes in Italy: Tectonic implications
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意大利历史地震的地震矩总和：构造意义
DOI：
10.1029/92jb00946
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发表时间：
1992
影响因子：
--
通讯作者：
R. Westaway
中科院分区：
文献类型：
--
作者：
R. Westaway
利用历史地震的宏观地震效应估计的地震矩，研究了意大利亚平宁山脉及其周围的构造形变速率。亚平宁北部(∼42.5°N以北)向东北伸展伴随着沿其东北侧翼的缩短。17世纪以来，这两个地区的稀有地震活动没有发生过6级以上地震或∼6×1018 N m以上的地震矩，其空间平均形变速率仅为∼0.3 mm yr−1，但相当，因此其外部环境的伸缩平衡，没有相对运动。相比之下，亚平宁中部和南部的许多历史地震，震级为∼7，地震矩∼为20×1018 N m，要求变形带的东北向相对速度高达∼5 mm yr−1，与其周围预期的相对运动相匹配。根据变形带的走向，这种相对速度部分由伸展作用获得，部分由走滑作用占据，在意大利其他地方并不伴随着梯队缩短。因此，亚平宁北部显示出与更南边的地方不同的意义和形变速率，因此与以前的解释相比，目前在技术上是不同的。
Tectonic deformation rates in and around the Apennine mountains of Italy are studied using seismic moments estimated from macroseismic effects of historical earthquakes. Northeastward extension in the northern Apennines (north of ∼42.5°N) accompanies shortening along their northeast flank. Since the seventeenth century, the sparse seismicity in these two zones has included no earthquake with magnitude >6.5 or seismic moment above ∼6×1018 N m. Their spatially averaged deformation rates are only ∼0.3 mm yr−1, but are equal, such that the extension and shortening balance with no relative motion between their external surroundings. In contrast, the numerous historical earthquakes in the central and southern Apennines with magnitude ∼7 and seismic moment ∼20×1018 N m require northeastward relative velocity across the deforming zone up to ∼5 mm yr−1, matching the expected relative motion of their surroundings. This relative velocity is taken up in part by extension and in part by strike-slip, depending on the trend of the deforming zone, and is not accompanied by en echelon shortening elsewhere in Italy. The northern Apennines thus show different senses and rates of deformation from localities farther south, and are thus technically distinct at present, in contrast with previous interpretations.