南海北部地震震源深度特征与岩石圈流变结构的关系研究
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摘要
利用收集的地震深度数据,讨论了南海北部及周缘陆区不同地壳结构地震震源深度的分布特征,结果表明:(1)华南大陆、大陆架、大陆坡区壳内地震分布的下界深度在30 km左右,平均深度华南大陆最浅、大陆架区次之,大陆坡区最深;(2)华南沿海大陆型地壳区地震集中分布于5￣15 km的“优势层”内;大陆架和大陆坡区地震的垂向分布也具有“优势层,”但厚度明显增加;而在南海海盆区,地震深度分布范围较大,有相当数量的地震分布于地幔内;(3)地震震源深度的分布特征与岩石圈热—流变结构密切相关,地震主要分布于地壳(岩石圈)的脆性层内。由于南海北部由陆向海脆性层底界深度加深,导致了地震“优势层”厚度加厚。(4)地壳上层的流变结构可能对南海北部及周缘陆区地震的发生有重要影响。
In this paper,the characteristics of the focal depth in the northern South China Sea are discussed.The statistic of the focal depth of the earthquakes shows that :(1) although from the South China Margin to the South China Basin the depth of Moho increases gradually,the depth for the border of the earthquakes distribution layer for every region in the northern SCS are adjacent,about 30 km.The average depth of the earthquakes in every region is different,the South China Sea Margin′s is shallowest;the South China Basin′s is deepest.(2) in the South China Margin most of the earthquakes occur in the depth of 5～15 km;in the continental shelf and continental slope of the northern SCS,there is also a seismogenic layer in the crust,but the thickness of this layer is thicker than that in the South China Margin;in the South China Sea Basin,the focal depths distribution is dispersed,some earthquakes occur in the mantle.(3) the characteristic of the focal depth is a good indicator of the the rheological structure of the lithosphere: the earthquakes occur in the brittle layer of the lithosphere.Because the base of the brittle layer burys more deeply from the South China to the South China Basin,the thickness of the seismogenic layer in the crust increases.(4) the rheological structure of the upper crust may be one of the main factors controlling the distribution of earthquakes in the northern South China Sea.
In this paper,the characteristics of the focal depth in the northern South China Sea are discussed.The statistic of the focal depth of the earthquakes shows that :(1) although from the South China Margin to the South China Basin the depth of Moho increases gradually,the depth for the border of the earthquakes distribution layer for every region in the northern SCS are adjacent,about 30 km.The average depth of the earthquakes in every region is different,the South China Sea Margin′s is shallowest;the South China Basin′s is deepest.(2) in the South China Margin most of the earthquakes occur in the depth of 5～15 km;in the continental shelf and continental slope of the northern SCS,there is also a seismogenic layer in the crust,but the thickness of this layer is thicker than that in the South China Margin;in the South China Sea Basin,the focal depths distribution is dispersed,some earthquakes occur in the mantle.(3) the characteristic of the focal depth is a good indicator of the the rheological structure of the lithosphere: the earthquakes occur in the brittle layer of the lithosphere.Because the base of the brittle layer burys more deeply from the South China to the South China Basin,the thickness of the seismogenic layer in the crust increases.(4) the rheological structure of the upper crust may be one of the main factors controlling the distribution of earthquakes in the northern South China Sea.
引文
[1]丁原章,梁劳.巴士系构造的地震危险性[J].华南地震,1992,12(2):1-14.
[2]魏柏林,冯绚敏,陈定国,等.东南沿海地震活动特征[M].北京:地震出版社,2001.
[3]刘以宣.南海新构造与地壳稳定性[M].北京:科学出版社,1994.
[4]张虎男.南海及周缘的地震活动与区域稳定性评价[J].海洋学报,1995,17(6):81-89.
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[11]马宗晋,薛峰.中国大陆地震深度分布与“易震层”初探[J].地震科学研究,1983,3(3):43-46.
[12]张国民,汪素云,李丽,等.中国大陆地震震源深度及其构造含义[J].科学通报,2002,47(9):663-668.
[13]汪素云.中国大陆地震震源分布特征的初步研究[J].地震研究,1996,19(3):310-314.
[14]吴富春,米秋霞.中国及邻区地震深度的特征[J].华北地震科学,1995,13(3):21-27.
[15]马宗晋.大陆多震层研究[C].北京:地震出版社,1992.
[16]夏戡原.南海的地壳类型及其分区[A].龚再升,李思田,夏戡原,等.南海北部大陆边缘盆地分析与油气聚集[C].北京:科学出版社,1997,14-23.
[17]施小斌,周蒂.南海北部陆缘岩石圈热-流变结构[J].科学通报,2000,45(15):1660-1665.
[18]龚再升,李思田.南海北部大陆边缘盆地油气藏动力学研究[M].北京:科学出版社,2004,30-36.
[19]Ranalli G,Murphy D C.Rheological stratification of the lithosphere[J].Tectonophysics,1987,132:281-295.
[20]Wang Y.Heat flow pattern and lateral variations of lithosphere strength in China mainland:Constraints onactive deformation[J].Physics of the Earth and Planetary Interiors,2001,126:121-146.
[21]Zhou D.Modeling of thermo-rheological structure of lithosphere under the foreland basin and mountain belt ofTaiwan[J].Tectonophysics,2003,374:115-134
[2]魏柏林,冯绚敏,陈定国,等.东南沿海地震活动特征[M].北京:地震出版社,2001.
[3]刘以宣.南海新构造与地壳稳定性[M].北京:科学出版社,1994.
[4]张虎男.南海及周缘的地震活动与区域稳定性评价[J].海洋学报,1995,17(6):81-89.
[5]林纪曾,谢明富,赵毅,等.东南沿海地区地震活动特征的研究[A].丁原章,李坪,时振梁,等.海南岛北部地震研究文集[C].北京:地震出版社,1988,173-184.
[6]邹和平.南海北部陆缘地震带的深部结构和孕震机制[J].华南地震,1998,18(3):16-20.
[7]胡圣标,汪集旸.闽台地区最大震源深度与地表热流的关系[J].地震地质,1993,15(1):66-68.
[8]万天丰,褚明记.闽台铲状活动断裂[J].地球科学,1987,12(1):21-28.
[9]李学波,李金森.汕头—吕宋岛岩石圈速度结构与震源构造—台湾浅滩7.3级地震构造之一[J].地球物理学进展,1996,11(1):28-41.
[10]施益忠.莫霍面及地壳结构[A].刘光鼎.中国海区及邻域地质地球物理特征[C].北京:科学出版社,1992,71-79.
[11]马宗晋,薛峰.中国大陆地震深度分布与“易震层”初探[J].地震科学研究,1983,3(3):43-46.
[12]张国民,汪素云,李丽,等.中国大陆地震震源深度及其构造含义[J].科学通报,2002,47(9):663-668.
[13]汪素云.中国大陆地震震源分布特征的初步研究[J].地震研究,1996,19(3):310-314.
[14]吴富春,米秋霞.中国及邻区地震深度的特征[J].华北地震科学,1995,13(3):21-27.
[15]马宗晋.大陆多震层研究[C].北京:地震出版社,1992.
[16]夏戡原.南海的地壳类型及其分区[A].龚再升,李思田,夏戡原,等.南海北部大陆边缘盆地分析与油气聚集[C].北京:科学出版社,1997,14-23.
[17]施小斌,周蒂.南海北部陆缘岩石圈热-流变结构[J].科学通报,2000,45(15):1660-1665.
[18]龚再升,李思田.南海北部大陆边缘盆地油气藏动力学研究[M].北京:科学出版社,2004,30-36.
[19]Ranalli G,Murphy D C.Rheological stratification of the lithosphere[J].Tectonophysics,1987,132:281-295.
[20]Wang Y.Heat flow pattern and lateral variations of lithosphere strength in China mainland:Constraints onactive deformation[J].Physics of the Earth and Planetary Interiors,2001,126:121-146.
[21]Zhou D.Modeling of thermo-rheological structure of lithosphere under the foreland basin and mountain belt ofTaiwan[J].Tectonophysics,2003,374:115-134
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