Interval velocity inversion method for earthquake waves

Abstract

The invention relates to an interval velocity inversion method for earthquake waves for processing earthquake exploration data, comprising the steps of receiving the data underground and obtaining VSP (Vertical Seismic Profiling) data, picking each first arrival and integer time, calculating the first arrival difference of adjacent integer sampling points, carrying out median filter wave field separation of the VSP data and obtaining down-going waves and leveling the down-going waves; opening one time window from the first sampling point; carrying out Fourier transform on a signal to obtain the phase spectrum of each frequency; getting the phase spectrum difference of the same frequency in adjacent channels; obtaining the first arrival second difference of non-integer sampling points of the adjacent channels by least square fit; summing the first arrival first difference and the first arrival second difference to obtain the first arrival difference; and obtaining the interval velocity by dividing the depth difference of the adjacent channels by the final first arrival difference of the adjacent channels. The method has strong ability resisting to immediate (random) interference; the algorithm is simple; and the inversion interval velocity has high precision.

Description

technical field [0001] The invention relates to a seismic exploration data processing technology, a method for inversion of seismic layer velocity by using the phase spectrum attribute of seismic data. Background technique [0002] In seismic exploration, because the shot point is very close to the wellhead, the vertical seismic profiling method (VSP) can be considered that the downgoing direct waves received at different depths have the same propagation path, and the interlayer time difference can be calculated directly by using the first arrival time, so as to reflect the It can provide a powerful method for surface seismic processing and interpretation. In the current VSP data processing, when the first arrival is picked, the seismic signal is firstly re-sampled in the time domain to increase the sampling rate. The specific method is to use the values ​​of several adjacent sample points to interpolate more sample point values, for example, interpolate a signal with a sam...

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Problems solved by technology

Since the interpolation itself is just a mathematical algorithm, the interpolated signal is not a real signal, which cannot improve the resolution of the original data. At the same time, the interpolation result is greatly affected by the interpolation method and the signal-to-noise ratio, which leads to the first arrival The picking accuracy is not enough, which restricts the application value of VSP data

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