地震所造成的沉積構造

全固結的沉積物受到地震作用的影響時，會破壞其靜態平衡，增加孔隙水壓，降低顆粒之間支撐的摩擦力，因而導致新的平衡產生。而在這變動瞬間會留下明顯的地質證據；這些證據包括：砂岩中的液化作用與頁岩中的搖變現象。所造成的沉積構造即所謂的沉積同時的變形構造，大多為脫水作用及重荷作用，其變形構造包括：沉積同時斷層、崩移構造、旋捲構造、侵入砂脈、球枕構造、荷重變形構造、砂火山、脫水構造、碟柱構造等。由於影響沉積同時的變形構造的因素很多，所以在討論沉積構造是否由於地震造成時，就必須特別注意以下幾點：（一）、沉積環境必須接近活動斷層帶；（二）、沉積物必須要有液化潛能；（三）、可以用實驗模擬的方式，做出同樣沉積構造；（四）、沉積構造儘量局限在單一的水平地層中；（五）、可從事大區域的對比；（六）、可對比於歷史紀錄；（七）、亦即最重要的一點，必須排除其他環境控制因素，諸如沖積扇、河成環境、潮間帶、三角洲、大陸棚、大陸斜坡等可能產生沉積物快速供應的環境；而湖相的沉積構造由於沉積物來源單純，沉積機制較容易控制，因此爭議較少，是相當適合古地震研究的沉積環境。

關鍵字

地震；沉積構造；液化；搖變

並列摘要

Earthquake will cause the unconsolidated sediments to lose their strength and become like viscous liquids. The mechanisms affecting this chang of state, from solid-like to liquid-like, are those of liquidization (sand) and thixotropy (mud). The structures induced by earthquake are called soft-sediment deformations. They include dish and pillar structures, water-escape sheets, sand volcanos, convolute lamination, load casts, ball-and-pillow structures, slumps, slides, and so on. Because they are identical to structures formed experimentally by simulated seismic shaking. Correlation of deformational structures with seismic events are based on: (1)proximity to presently active seismic zones; (2)presence of potentially liquefiable sediments; (3)similarity to structures formed experimentally; (4)small-scale internal structures within deformed zones that suggest liquifaction; (5) structures restricted to single stratigraphic intervals; (6) zones of structures correlatable over large areas; and (7)absence of detectable influence by continental slopes, alluvial fans, delta, channel shift, tidal flats, or other sedimentologically deformational process. And this method is perfactly applied to lake sediments.

並列關鍵字

Earthquake ； sedimentary structure ； liquidization ； thixotropy

國際替代計量

地震所造成的沉積構造

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