【作者】 于泳；

【导师】 洪汉净；

【作者基本信息】 中国地震局地质研究所 ， 固体地球物理学， 2002， 博士

【摘要】 地壳内部大多数强震是构造地震，是构造活动的产物。地震的发生主要与断层的稳定性而不是介质的强度有关。作为地壳块体的边界，断层的失稳还与其周围的块体的运动与变形有关。因而除了要理解断层失稳机制，模拟断层的失稳与强震的发生外，还要理解构造活动的规律，特别是在板块运动作用下板内变形的规律，进而模拟它的构造运动与失稳。论文从地震活动性分析出发，通过统计与数值模拟的方法分析了全球主要地震带、我国大陆地震区、构造扭结点的地震时空演化规律，模拟了强震主体地区的形成与分布，考虑了脆韧性层的应力传递与动态相互作用，建立了模拟地块与断层运动体系的粘弹性有限元与弹簧滑块耦合模型的数值模拟方法，引入了模拟断层滑动非均匀的滑动速率分配耦合模型，并模拟了川滇菱形地块的运动与边界断裂的地震模式。实现了研究缓慢的大尺度的大陆地壳构造变形转化为急剧的小尺度断层失稳的模拟过程，并进行了理论模型的模拟和实际应用。 比较了环太平洋带和地中海—喜马拉雅带强震活动的变化规律，在茂木清夫划分的1897-1916、1917-1933、1934-1951和1952-1970年四个时间段基础上，划分出1952-1971、1972-1979、1980-1998，1999-2002年四个时间段。地中海—喜马拉雅带的特大地震分布，明显呈现活跃和相对平静的时间分段性。北太平洋地震带与地中海-喜马拉雅带有较好的互补关系。在地中海-喜马拉雅带地震活跃的时间段内，与西南太平洋带、东南太平洋带共同构成了横跨南北半球与近纬向分布的强震带。在北太平洋地震活跃时，与西南、东南太平洋带共同构成了环太平洋地震带。 我国大陆及邻近区域的四个构造扭结点阿萨姆、帕米尔、珲春深震区、台湾的地震活动占据了大陆地震的主要份额，表现了微动态的活动特征。珲春深震区与台湾同属于西太平洋构造带，欧亚板块东部，所以地震特征表现出一定的相似性。帕米尔区相对于阿萨姆地震活动频繁，能量积累和释放的时间较短。由于两个区域同属于相同的板块边缘，两端的涨落有着基本一致的形式。构造扭结点的地震活动一定程度上影响了大陆内部地震的活动性。 采用了三维粘弹性耦合模型模拟印度与欧亚大陆碰撞条件下，我国大陆强震区的形成和地震空间分布的非均匀性，强调了深部韧性层屈服对脆性层应力积累的影响和欧亚板块对推挤的限制作用。模拟的粘弹性应力分布与实际地震统计的应变能释放分布情况比较得到了较好的符合情况，描述了我国强震分布区域，主要是在印度次大陆的长期推挤，高原巨厚地壳及其弱化的下地壳为弹性层的应力集中创造了条件，长距离的挤入是碰撞带两犄角的变形不断延伸，形成了两侧的变形梯度带。 为了理解地壳的脆韧性分层耦合的应力传递关系，采用脆韧性耦合模型模拟了剪切边界条件的应力分布与Kusznir模型相比，可说明我国大陆地震区的形成主要成因于印欧板块的宽泛边界的推挤作用。结合常应力边界条件和常速度边界条件的非均匀脆韧耦合模型模拟的结果对比，在不同的应力环境下，脆韧耦合模型的应力传递过程不仅体现在垂向，而且由于脆韧性层界面的应变差异也会形成不同介质区域横向的应力非均匀，而这种深部的非均匀性也将体现在上覆脆性层中。脆韧耦合决定了应力向脆性层的快速集中，深部韧性层的介质非均匀决定了脆性层应力的空间分配与演化过程。 走滑断层与逆冲断层震后的应力演化与再分配的模拟说明，地震并不是脆性上地壳层的孤立行为，整个地壳层甚至是岩石圈都参与了地震的孕育、发生和循环过程‘地震的终极动力来源于深部地慢的运动，板块边界成为直接作用于大陆的力源，但其中大陆中下地壳的结构和介质性质的特点决定了应力分配与调节机制。 建立了粘弹性有限元方法和弹簧滑块的祸合模型，通过位移和应力的传递实现了两种方法的祸合计算。并且可以模拟多条断层与块体运动的复杂体系。模拟断层的弹簧滑块模型给出服从Gutenberg一形chter频度震级关系的地震序列;地震破裂过程由成核点开始向两端扩展，作为成核点的初始滑块的应力状态控制了发震时间和地点，但是事件的尺度并不是由成核点决定的，取决于破裂扩展中其它滑块的应力状态和强度分布，并与地震波反演的地震破裂过程进行了对比;匀阻段与摩擦随机分布模型的地震应力降标度关系符合幂指数关系叮ocM了的数学关系，应力降是随着地震的尺度增加而增加，中强震以上的应力降保持在零点JL巴到两个巴之间。 断层应力与地震的对比说明断层的应力状态取决于地震的活动方式，地震的平静对应断层的应力积累，但地震的活跃并不一定是断层应力降低的表现。断层的破裂事件释放了地壳块体的部分应力，并使近断层的应力得到重新调整，而地块的应力状态受到断层整体地震活动的控制。单个地震的发生产生了同震应力的分布，它是断层与地块间应力传递的途径。地块应力受到断层应力控制的结果使得整个地壳处于高应力积累的状态，这为地块内部断层的地震发生准备了应力条件。 多断层与地块祸合模型的模拟进一步认识了地壳复杂体系的动力演化过程。地块成为断层间相关的桥梁，虽然每一条断层的地震活动仍然受更多还原

【Abstract】 Earthquakes in the continental lithosphere are the result of tectonic motion. Seismicity is related to stability of fault rather than its strength. Rupture of fault which occurs on the boundary of a crustal block is a consequence of motion and deformation of tectonic plates. For studying mechanism of rupture of fault, deformation of interior plate by tectonic motion should be considered. In this paper, energy statistics is used to analyze the spatial and temporal distribution of earthquakes around the world, China continental seismic regions and tectonic twist nodes. Distribution of seismic regions is simulated by a viscoelastic two-layer model. Transfer of stress and dynamic interaction in the viscoelastic crust are studied by numerical simulation under various kinds of boundary conditons. A numerical method of the finite element coupled with spring-block model is developed to simulate the system of faults and crustal blocks. Heterogeneous slip of a fault can be studied with distributed velocity un the spring-block model. The coupled model is applied to analyze the dynamics of movement of the Chuandian block and seismicity on boundary faults. The coupled model provides a way to link slow motion of a large-scale continental plate with sudden small-scale rupture of faults. It can be used for theoretical and practice application.The active and inactive periods of the world seismic zones are discussed further. The temporal change of great earthquakes in the circum-Pacific belt and Mediterranean-Himalayan belt is examined. There are eight periods which are more than that proposed by Mogi in last century. These periods are 1897-1916, 1917-1933, 1934-1951, 1952-1970, 1952-1971, 1972-1979, 1980-1998 and 1999-2002. In the Mediterranean-Himalayan seismic zone, the activity of great earthquakes is remarkably high during periods 1897-1917, 1934-1951, 1972-1979 and 1999-2002, appreciably low in the periods 1917-1933, 1952-1971 and1980-1998. The northern Pacific seismic belt is active in the inactive periods of Mediterranean-Himalayan seismic zone. The activities of southwest and southeast Pacific belts do not show such a regular pattern. So during different periods, there are two types of seismic distribution around the world. One is the circum-Pacific belt, and another is the latitudinal belt which joining the Mediterranean-Himalayan seismic zone with southwest and southeast Pacific belts. These results suggest that large earthquakes are strongly coupled on a global scale.There are four tectonic twist nodes, i.e. Asam, Pamir, Hunchun and Taiwan, around China continent. The seimic activity in these areas can be devided into micro-dynamic periods. The Hunchun deep earthquake zone and Taiwan are located in the west-Pacific tectonic belt of the eastern Eurasia plate. So they have similar temporal seismic characteristics. The periods of accumulation and release of stress in Pamir are shorter than those in Asam. The activity of tectonic twist nodes sometimes is related with space-time distribution of intracontinent earthquakes.For understanding the transfer of stress of the brittle-ductile model, a simplified model of two-layer viscoelastic lithosphere is built. Shear stress is applied on its boundary. The result comparison with Kusznir’s model demonstrates that theIndia-Eurasia collision affects the wild deformation of China continental seismic zones. The heterogeneous brittle-ductile models with constant stress and constant velocity boundary conditions show that stress transfers from the ductile layer to the brittle layer, and the heterogeneous ductile layer also affects stress distribution of the brittle layer. The stress would be heterogeneous in the brittle layer along horizontal direction because strain difference of layer’s interface controls transfer process of stress. As a conclusion, the brittle-ductile coupling produces the quick transfer of stress, and the deep heterogeneous ductile layer generates stress distribution and dynamic process in the brittle layer.Stress process and redistribution of a strike-slip更多还原