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Geophone orientation and coupling in three‐component sea‐floor data: a case study [Note 1. Received April 1998, revision accepted March 1999. ...]
Author(s) -
Li XiangYang,
Yuan Jianxin
Publication year - 1999
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1046/j.1365-2478.1999.00160.x
Subject(s) - geophone , geology , gemology , regional geology , orientation (vector space) , seabed , economic geology , geodesy , engineering geology , geophysics , seismology , geometry , metamorphic petrology , mathematics , tectonics , oceanography , volcanism
We analyse the geophone orientation and coupling in a data set from the North Sea. Based on the polarization of the water‐break on the sea‐floor, we have derived processing algorithms for determining the receiver orientation for gimballed and non‐gimballed geophone systems. For a gimballed system, the problem reduces to a simple horizontal rotation. However, for a non‐gimballed system, where all three geophone axes may vary due to varying acquisition conditions such as dipping sea‐floor, twisting of recording cable, etc., the three orientation angles cannot be found directly from the recorded displacement vectors. Using the data redundancy within a common‐receiver gather, a robust two‐stage method is derived for the non‐gimballed system in which all three orientations can initially be unknown. Testing on the North Sea data set acquired with a gimballed system shows that the three‐component geophones in the data set are orientated satisfactorily within an error of 5°. However, there are some undesirable cross‐couplings between the vertical and horizontal geophones, which results in leakage of shear‐wave energy from the horizontal components to the vertical components.