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在 1679年三河 -平谷 8 0级大震的震源区布置了两条总长 140km ,2 4次覆盖的近垂直深地震反射剖面 ,剖面穿过夏垫断裂及二十里长山断裂。结果表明 ,该区以双程走时 7 0s(2 1km)左右和 11 0～ 12 5s(33～ 37km)左右的两个强反射叠层把地壳分为上地壳、下地壳和壳幔过渡带 ;地壳结构在纵向上差异较大 ,浅部成层性较好 ,层组较多 ,结构复杂 ;上地壳总体呈反射“透明”性质 ,下部地壳表现为明显的反射性质 ;在横向上也具有明显的差异 ;深部断裂主要有夏垫断裂下方的地壳深断裂 ,断层面较陡 ,近于直立 ,该断裂可能为三河 -平谷 8 0级大地震的发震断裂 ;分别在两条剖面下地壳和上地壳下部存在局部强反射能量团 ,应为上地幔物质上涌冷却形成的岩墙或岩体 ;由于该处的岩浆活动造成了局部应力分布的差异 ,导致了地壳深断裂的形成 ,这可能是三河 8 0级大震的深部构造背景
Two near-vertical deep seismic reflection sections covering 140km and 24 times are arranged in the source area of the M80-M80 magnitude earthquake in 1679. The section crosses the Xia pad and the Twenty-mile Changshan fault. The results show that the crust is divided into the upper crust, the lower crust and the crust - mantle transitional zone by two strong reflection stacks of about 70s (21km) and 11 0 ~ 125s (33 ~ 37km). The crustal structure differs greatly in the longitudinal direction, with shallow stratigraphic formations, more layer sets and complex structures. The upper crust is generally “transparent” in reflection and the lower crust exhibits obvious reflexive properties, and also shows obvious horizontal . The deep faults mainly include the deep crustal crust beneath the Xia pad, and the fault plane is steep and nearly upright. This fault may be the seismogenic fault of the Sanhe-Pinggu M88 earthquake. The crustal and The presence of locally strongly reflecting energy clusters in the lower part of the upper crust should be the dikes or rock masses formed by upwelling of the upper mantle material. The differences in local stress distribution caused by the magmatism there may lead to the formation of deep crustal crusts, which may It is the deep tectonic background of the M8080 earthquake