摘要
目前世界上用地震方法研究地壳结构,通常借助于广角反射或折射,即地震地壳测深方法,研究对象主要是莫霍面及其上覆层的粗略结构。研究地壳的另一种方法是采用长排列的反射波多次叠加技术。如美国从七十年代开始进行的大陆地壳深反射剖面(COCORP)测量,能较好地研究深部地壳结构,揭露深部重要的地质现象。但其讯噪比及分辩力还有待提高。本文所介绍的全地壳地震反射剖面是以宽线技术为基础,结合大陆地壳深反射剖面的某些技术特点,而形成一种新的反射地震剖面。它不仅对中、浅层反射有较高的讯噪比和分辩力,而且对深部地壳反射同样有效。研究表明,浅部多次反射波由于吸收作用所造成的强烈衰减远大于同时间到达的深部一次反射波,因而在较短排列情况下(2000米左右)也能有效地研究包括莫霍面在内的深部地壳反射。所得剖面能作全地壳整体解剖,并与找油气(或找矿)密切结合起来,从而以低廉的附加费用取得深部资料。鉴于工作方法及剖面特点有别于大陆地壳深反射剖面(COCORP),故称为“全地壳地震反射剖面”。本文着重介绍它的方法技术特点及地质效果,并论证了该方法的有效性与可行性。
Abstract
Nowadays the wide angle reflection/refraction-the deep-crustal sounding is usually used as a seismic method in the world mainly for Studying rough structure of Moho & its overling beds. The multi-stacked technique of reflection events with long spread is another way to study the earth-crustal structures. For instance, the "CO-CORP", having been engaged in America since the beginning of 1970's, is quite useful for studying the deep-crustal struture and revealing the important deep-crustal geological phenomena. However, the S/N ratio and resolution remain to be improved for the "COCORP". The whole crustal seismic reflection profile (WCSRP) technique recommended here in this paper is based on the wide line profiling and combined with certain features of COCORP, thus becoming a new type of seismic reflection profile. The WCSRP has a high S/N ratio & resolution not only for middle or shallow reflections but for the deep-crustal reflections, The profile as mentioned above can serve as the whole crustal dissection, and the information could be obtained at less additional expenses if combined with the oil/gas prospecting. This seismic profile could be called WCSRP because it has special proceedings and features different from the COCORP.
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