Optical fiber multi-channel seismic system for detecting stratum transverse wave velocity structure in extremely shallow sea area

Abstract

The invention discloses an optical fiber multi-channel seismic system for detecting a stratum transverse wave velocity structure in an extremely shallow sea area. The system comprises an gas explosionsource used for exciting strong energy in a shallow sea land area and a seabed, a distributed acoustic sensing optical fiber array used for sensing a seabed stratum strain and a stress change, and ademodulation recording unit used for demodulating external strain stress field information sensed by the distributed acoustic sensing optical fiber array into seismic wave signals and realizing continuous acquisition, recording and storage. The distributed acoustic sensing optical fiber array comprises an optical fiber starting end, an optical fiber connecting section, an optical fiber array and an optical fiber tail end; and linear display cloth, Z-shaped display cloth or O-shaped display cloth can be adopted. A sensing distance reaches 10 kilometers, a channel spacing is dynamically adjustable, and the number of collected seismic channels reaches ten thousand so that the system is easily suitable for high-density space sampling of seabed transverse wave signals in the extremely shallow water area; and meanwhile, the system has the advantages of ''streamer earthquake'' multi-channel observation and long-time continuous recording of an ''ocean bottom seismograph'', and transverse wavespeed information which cannot be obtained by a traditional streamer earthquake can be observed.

Description

technical field [0001] The invention relates to an optical fiber multi-channel seismic system for detecting the shear wave velocity structure of formations in extremely shallow sea areas, and belongs to the fields of marine geophysics and marine geology. Background technique [0002] The extremely shallow sea area (the water depth is less than 5 meters) is the suture zone where the earth's land and the ocean meet, and is most closely related to the range of human activities. Almost every large-scale offshore engineering construction of human beings, such as submarine tunnels, cross-sea bridges, sea airports, For marine playgrounds, etc., it is necessary to understand the shallow submarine geological structure of the construction area and evaluate the stability of the seabed. The shear wave velocity structure is an important parameter for evaluating the bearing capacity of the formation and the degree of fracture development. Nowadays, the most common marine survey equipment ...

AI Technical Summary

Problems solved by technology

Nowadays, the most common marine survey equipment in the world is the streamer multi-channel seismic system. Due to the limitation of the navigation depth of the mother ship and the influence of shallow sea reefs, platforms, ships and other obstacles, it is difficult to achieve stratigraphic detection operations in extremely shallow seas, and There are problems such as large track spacing, sparse spatial sampling, and only reflected longitudinal waves can be observed on the sea surface, so it is impossible to detect the shear wave velocity structure of the seabed formation.

At present, my country's seismic observation technology that can obtain seabed shear wave information mainly includes submarine seismographs, submarine nodes, submarine cables, and submarine observation networks. The number of sensors is proportional, the sampling interval is more sparse, and the price is expensive. It is impossible to obtain small-track spacing and high-density seismic data. It is only suitable for large-scale earth structure research or marine oil and gas resource detection.

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