Crustal seismicity and the earthquake catalog maximum moment magnitude (Mcmax ) in stable continental regions (SCRs): Correlation with the seismic velocity of the lithosphere
Crustal seismicity and the earthquake catalog maximum moment magnitude (Mcmax ) in stable continental regions (SCRs): Correlation with the seismic velocity of the lithosphere
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DOI：
10.1016/j.epsl.2012.08.032
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发表时间：
2012-12
影响因子：
5.3
通讯作者：
W. Mooney;J. Ritsema;Y. K. Hwang
中科院分区：
文献类型：
--
作者：
W. Mooney;J. Ritsema;Y. K. Hwang
对全球地震活动和地震层析成像的联合分析表明，大陆板内地区的地震潜势与岩石圈的地震性质有关。太古代和早元古代的地壳活动具有冷的、稳定的大陆岩石圈根，地壳地震较少，最大地震目录矩震级（Mcmax）较低。从全球地震模型S40RTS中推断出岩石圈厚根的地理分布，该模型显示了相对于初步参考地球模型（PREM）的剪切速度扰动（δVS）。我们将175km深度处的δ VS与地壳中板内地震的位置和矩震级（Mw）进行了比较（Schulte和Mooney，2005）。许多板内地震集中在岩石圈厚度明显的横向梯度周围，这些梯度围绕着板块，很少有地震发生在板块内部。在全球范围内，27%的稳定大陆岩石圈位于δVS≥ 3.0%的区域之下，而Mw>4.5的地壳地震只有6.5%发生在这些岩石圈厚区之上。在δVS> 3.5%的地幔岩石圈之上，虽然地幔岩石圈占稳定大陆区的19%，但在我们的目录中没有发生Mw>6的地震。因此，对于具有地震确定的厚岩石圈的地壳内部，（1）地壳地震的数量显著减少，（2）地震目录中发现的最大矩震级为Mcmax=6.0。我们将这些观测结果归因于下地壳和高度枯竭的岩石圈根的温度较低和脱水，导致岩石圈强度较高。
A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVSat a depth of 175km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.