CN-122018006-A - Submarine earthquake positioning method utilizing submarine cable seismic wavefront through linear communication

CN122018006ACN 122018006 ACN122018006 ACN 122018006ACN-122018006-A

Abstract

The invention discloses a submarine seismic positioning method utilizing a linear communication submarine cable seismic wavefront, which comprises the following steps of acquiring a geographic coordinate and an S-wave speed model of each receiving channel of a submarine cable before an earthquake, acquiring a space-time-strain rate diagram of the submarine cable after the earthquake, acquiring a first seismic wave according to the space-time-strain rate diagram, acquiring wavefront information of the earthquake on the submarine cable according to the first seismic wave, constructing a differential equation representing the relation between the distance along an optical cable and the component of the seismic wave propagation speed along the optical fiber direction by utilizing a linear wavefront method based on the S-wave speed model, acquiring the position relation between a seismic center position and a submarine cable reference point according to the differential equation and the wavefront information, and acquiring the coordinate of the seismic center position according to the geographic coordinate of each receiving channel of the submarine cable and the position relation between the seismic center position and the submarine cable reference point. The invention solves the problem of insufficient positioning precision of submarine earthquake caused by insufficient coverage of OBS in ocean by using the active submarine communication optical cable and the distributed acoustic sensing technology.

Inventors

LI CHAOHUI
YUE BING
CHEN SHAOYI
LI TIANRUI
HUANG PENGFEI

Assignees

中山大学
南方海洋科学与工程广东省实验室(珠海)

Dates

Publication Date: 20260512
Application Date: 20251128

Claims (10)

1. A submarine seismic positioning method utilizing a linear communication submarine cable seismic wavefront is characterized by comprising the following steps: Acquiring a space-time-strain rate diagram of the submarine cable after the earthquake; acquiring a first seismic wave according to the space-time-strain rate diagram; According to the first seismic wave, wavefront information of the earthquake on the submarine cable is obtained; Constructing a differential equation representing the relation between the distance along the optical cable and the component of the seismic wave propagation speed along the optical fiber direction by using a linear wave front method based on the S-wave speed model; Obtaining the position relation between the seism position and a submarine cable reference point according to the differential equation and the wave front information, wherein the submarine cable reference point is a submarine cable endpoint; and obtaining the coordinates of the seismometer position according to the geographical coordinates of each receiving channel of the submarine cable and the position relation between the seismometer position and the submarine cable reference point.
2. The submarine seismic localization method using the linear communication submarine cable seismic wavefront according to claim 1, wherein the S-wave velocity model of the submarine cable vicinity investigation region is obtained from an AK135 model.
3. The submarine seismic localization method using a linear communication submarine cable seismic wavefront according to claim 1, wherein obtaining the wavefront information of the seismic on the submarine cable according to the first seismic wave comprises: performing density analysis on the power spectrums of the first seismic wave before and during seismic wave reception to obtain a signal enhancement frequency band when the seismic wave arrives; according to the signal enhancement frequency band, carrying out band-pass filtering on the first seismic wave to obtain a second seismic wave; And carrying out seismic phase travel time extraction on the second seismic wave to obtain the wave front information of the earthquake on the submarine cable.
4. The method for locating a submarine earthquake using a linear communication submarine cable seismic wavefront according to claim 3, wherein performing the seismic phase travel time extraction of the second seismic wave to obtain the wavefront information of the earthquake on the submarine cable comprises: and inputting the second seismic wave into PhaseNet-DAS neural network to obtain the wavefront information of the earthquake on the submarine cable.
5. The submarine seismic localization method using a linear communication submarine cable seismic wavefront according to claim 4, wherein constructing a differential equation representing a relationship between a distance along an optical cable and a component of a seismic wave propagation velocity along an optical fiber direction using a linear wavefront method based on the S-wave velocity model comprises: the calculation formula of the component of the propagation velocity of the seismic wave along the optical fiber direction is as follows: In the formula, A component representing the propagation velocity of the seismic wave along the direction of the optical fiber; Representing an S-wave velocity model, representing the actual propagation velocity of the seismic wave; Representing the azimuth angle between the position of a certain virtual sensor element on the submarine cable and the propagation direction of the seismic wave, wherein tan theta= (x+l)/D, L is the horizontal distance from the position of the earthquake to the submarine cable reference point, and D represents the vertical distance from the earthquake to the submarine cable reference point; Will be With respect to distance along cable And performing second order derivation to obtain the differential equation: 。
6. the submarine seismic localization method using the linear communication submarine cable seismic wavefront according to claim 5, wherein obtaining the positional relationship between the epicenter position and the submarine cable reference point according to the differential equation and the wavefront information comprises: solving the differential equation to obtain a first expression; integrating the first expression with respect to time to obtain a second expression; and obtaining the position relation between the epicenter position and the submarine cable reference point according to the wavefront information and the second expression.
7. The ocean bottom seismic localization method using a rectilinear communications ocean cable seismic wavefront of claim 6, wherein the first expression is: In the formula, Representing a constant.
8. The ocean bottom seismic localization method using a rectilinear communications ocean cable seismic wavefront of claim 7, wherein the second expression is: In the formula, Indicating distance along the cable The arrival time of the received seismic signal, given by the wavefront information, Representing the arrival time of the seismic signal received at the sea cable reference point.
9. The submarine seismic localization method using the linear communication submarine cable seismic wavefront according to any one of claims 5 to 8, wherein obtaining coordinates of the center of the earthquake position from the geographical coordinates of each receiving channel of the submarine cable and the positional relationship of the center of the earthquake position to the submarine cable reference point comprises: According to D and L are calculated, and longitude and latitude difference values of the seismometer position relative to the submarine cable reference point are obtained; and obtaining coordinates of the seismometer position according to the latitude and longitude of the submarine cable reference point and the latitude and longitude difference value of the seismometer position relative to the submarine cable reference point.
10. The submarine seismic localization method using the linear communication submarine cable seismic wavefront according to claim 9, wherein obtaining coordinates of the center of the earthquake position according to the latitude and longitude of the submarine cable reference point and the latitude and longitude difference value of the center of the earthquake position relative to the submarine cable reference point comprises: And adding the longitude and latitude difference value of the seismometer position relative to the submarine cable reference point to the longitude and latitude of the submarine cable reference point to obtain the coordinate of the seismometer position.

Description

Submarine earthquake positioning method utilizing submarine cable seismic wavefront through linear communication Technical Field The invention relates to the technical field of submarine seismic positioning, in particular to a submarine seismic positioning method utilizing a linear communication submarine cable seismic wavefront. Background Currently, high-precision monitoring is performed on submarine seismic activities, particularly on seismic clusters with clustered seismic characteristics, and the high-precision array system arranged on the seabed is mainly relied on, and the core equipment of the high-precision array system is a submarine seismograph. The technical system aims to realize accurate inversion of core parameters such as a seismic source space position, a transmission focal depth degree, a fault fracture mechanism and the like by capturing key seismic phases such as P waves, S waves and the like generated by an earthquake, thereby providing vital data support for seismic mechanism research, tsunami early warning and marine geological structure exploration. However, although the technology is mature in principle, in practical large-scale application and business operation, a series of serious challenges brought by complex marine environments are faced with ① equipment layout and survival challenges, namely that the deployment and recovery of the submarine seismograph are seriously dependent on expensive scientific research ship operation. Under severe sea conditions, accurate placement and long-term in-place stability of equipment face great challenges. The factors such as the complicated topography of the seabed, strong ocean current impact, marine organism adhesion, bottom sediment migration and the like can cause equipment displacement, overturning and even damage, and the reliability of data acquisition is obviously reduced. ② The technical bottleneck of data real-time transmission is that most of the existing submarine seismographs adopt a self-contained working mode, namely, the data are stored in equipment after being collected, and the data are recovered and downloaded after the task period is finished. The method causes serious delay in seismic data acquisition, and cannot meet urgent requirements of tsunami warning and other applications on real-time performance. Although a real-time transmission system based on the submarine optical cable exists, the construction and maintenance cost of the real-time transmission system is astronomical digital, the technical complexity is high, the real-time transmission system is difficult to popularize on a large scale, and a huge gap between monitoring capability and real-time requirements is formed. ③ The high full cycle cost limits, namely the cost of the whole technical chain from the research and development and manufacturing of equipment, the deployment of offshore operation, long-term operation and maintenance and data recovery are extremely high. This directly limits the number of stations that can be put into service, resulting in limited coverage of the monitoring network, a far lower array spacing (i.e., coverage density) than Liu Detai networks, and further in insufficient positioning accuracy for ocean bottom earthquakes. Disclosure of Invention The invention provides a submarine earthquake positioning method utilizing a linear communication submarine cable seismic wavefront, which solves the problems that a large amount of effective submarine earthquake data cannot be obtained due to insufficient coverage density of a submarine seismograph (OBS) in the prior art and the submarine earthquake positioning precision is insufficient due to the fact that a single submarine cable cannot obtain accurate S-wave travel time difference. In order to solve the technical problems, the technical scheme of the invention is as follows: the invention provides a submarine seismic positioning method utilizing a linear communication submarine cable seismic wavefront, which comprises the following steps of: Acquiring a space-time-strain rate diagram of the submarine cable after the earthquake; acquiring a first seismic wave according to the space-time-strain rate diagram; According to the first seismic wave, wavefront information of the earthquake on the submarine cable is obtained; Constructing a differential equation representing the relation between the distance along the optical cable and the component of the seismic wave propagation speed along the optical fiber direction by using a linear wave front method based on the S-wave speed model; Obtaining the position relation between the seism position and a submarine cable reference point according to the differential equation and the wave front information, wherein the submarine cable reference point is a submarine cable endpoint; and obtaining the coordinates of the seismometer position according to the geographical coordinates of each receiving channel of the submarine cable and the position relatio