Traveltime tomography seismic inversion geoscienceworld. Inversion of travel times and seismic waveforms springerlink. One hundred training sets were created by randomly varying the velocity of one of the four interior cells. Adaptation of back projection tomography to seismic travel. Joint full waveform inversion and travel time tomography. The problem is nonlinear, and therefore optimization techniques have been used to find a reasonable solution to the problem. The main problem in fitting the data is the lack of low spatial frequencies. In this study, refraction seismic tomography was using wavepath eikonal traveltime wet inversion. The inverse problem in tomography is then to manipulate m in order to. So, for a common midpoint cmp gather, tomography will try to account for the travel time.
By continuing to use our website, you are agreeing to our use of cookies. Waveequationbased traveltime seismic tomography part. Application of seismic travel time tomography request pdf. High resolution seismic refraction tomography for determining. Detection of systematic errors in traveltime data using a. The inversion of seismic travel time data for radially varying media was initially investigated by herglotz, wiechert, and bateman the hwb method in the early part of the 20th century 1. The goal of seismic travel time tomography is to find a velocity model for a subsurface volume consistent with measured travel times along ray paths that pass through the volume. A new recursive inverse scheme is applied to a currently popular problem named seismic travel time tomography, in order to enhance the efficiency and reliability in obtaining a new velocity model if a small number of new data are added to a large data set in the past. Seismic traveltime tomography is a geophysical inversion method which is used to obtain the physical parameters such as velocities of longitudinal wave and shear wave, quality factor and anisotropic parameters by use of a large number of seismic dataset. This paper describes the application of tomography to seismic travel. In seismic tomography, travel time residuals defined as differences.
Central brazil, and especially the tocantins province, is one of the most complex tectonic regions in south america. Jul 04, 2016 full waveform inversion fwi is a process in which seismic numerical simulations are fit to observed data by changing the wave velocity model of the medium under investigation. Travel time and amplitude analysis in seismic tomography. Pdf travel time inversion of marine seismic data for. Causes of intraplate seismicity in central brazil from travel. The depth of the sea floor is estimated by the reflection tomography at first, and then the velocity distribution in the sea water is computed by travel time inversion of both transmitted and. Quintero abstract many seismological studies depend on the accuracy of timing of seismological data. Bianco, student member, ieee, peter gerstoft, member, ieee, abstractwe develop a 2d travel time tomography method which regularizes the inversion by modeling groups of slowness pixels from discrete slowness maps, called patches, as sparse linear combinations of atoms from a dictionary. Waveequationbased travel time seismic tomography is rooted in the following tomographic equation tobs tsyn d z k. Integrated seismic processing challenges in karstified.
Seismic tomography and the assessment of uncertainty. Adaptation of back projection tomography to seismic travel time problems eugene humphreys 1 and robert w. The use of gradient methods of optimization allows to solve largesized least squares inverse problems iteratively. In the framework of the geometric optics approach to seismic problems, the travel time t r, r j of the seismic ray can be. Jun 24, 2014 a new recursive inverse scheme is applied to a currently popular problem named seismic travel time tomography, in order to enhance the efficiency and reliability in obtaining a new velocity model if a small number of new data are added to a large data set in the past. Improvements of traveltime tomography models from joint. We used an accelerometer with lat frequency response to. Local earthquake traveltime tomography mountain building. A method of seismic traveltime inversion for simultaneous determination of 2d velocity and interface structure is presented that is applicable to any we use cookies to enhance your experience on our website. It has been the primary means for earthquake imaging of the earths interior from the early 1970s. Both the travel time and amplitude tomography methods are applied here to field data from a cross. High resolution seismic refraction tomography has proved to be a useful tool to effectively estimate depth of blast induced damage in a mine face. Seismic traveltime inversion for 2d crustal velocity.
The data received at seismometers are used to solve an inverse problem, wherein the locations. Then a joint inversion of firstarrival and reflection traveltimes for imaging seismic velocity structures in complex terrains is presented. This time we shall focus on the traveltime tomography, look into the details inside this approach, and discuss key technical issues. However, traveltime inversions still result in smoothed solutions and for. Pdf seismic traveltime inversion based on tomographic equation. Prospeccio sismica tomografia sismica seismic prospecting seismic tomography. Travel time inversion in seismic tomography computer science.
There are various implementations of traveltime tomo graphy. Our final preferred velocity model shows a good correspondence with regional geological units. As discussed in chapter 1, geophysical traveltime tomography is the procedure for inverting traveltimes of specified body waves for the velocity distribution of the earth. In waveform inversion, each iteration consists on a backpropagation of the waveform residuals. In travel time inversion, each iteration consists on a backprojection of the travel time residuals. This is a form of seismic traveltime inversion that is used to. Seismic traveltime inversion based on tomographic equation. Article application of wavelet denoising for traveltime.
Ray tracing applied to travel time seismic tomography. Seismic traveltime inversion for 2d crustal velocity structure. Full waveform inversion guided by travel time tomography. Causes of intraplate seismicity in central brazil from. Threedimensional seismic tomography from p wave and. Xianhuai zhu to present case studies using tomography approach. Travel time ray tomography tomography sets out to determine the interval velocity back along the individual raypaths, rather than using the false 1d assumption that the update can be purely vertical lines and treitel, 1985. Travel time tomography with adaptive dictionaries michael bianco, student member, ieee, peter gerstoft, member, ieee, abstractwe develop a 2d travel time tomography method which regularizes the inversion by modeling groups of slowness pixels from discrete slowness maps, called patches, as sparse linear combinations of atoms from a dictionary. Significant structural heterogeneities are revealed in the crust of the 1992 landers earthquake area which may be closely related to the local seismic activities. Inversion of multichannel seismic data by combination of travel time and fullwaveform tomography. In the usual implementation of reflection traveltime tomography, the model parameters are perturbed while preserving the offset values of the seismic data section j.
In travel time inversion of crosshole seismic tomography, when dealing with real data, the following three issues need to be addressed. Clayton seismological laboratory, california institute of technology, pasadena a back projection method of reconstruction is adapted to invert seismic travel time data for velocity structure. Pdf travel time crosshole seismic tomography is applied to. From the synthetic data studies it was not possible to unequivocally demonstrate. This paper describes the application of tomography to seismic traveltime inversion. Improvements of traveltime tomography models from joint inversion of multichannel and wideangle seismic data slaven begovic 1, cesar ranero 2, valenti sallares 1, adria melendez 1, and ingo grevemeyer 3. In comparison with conventional inverse schemes in seismic tomography, either leastsquares or iterative types, this scheme. Application of tomography inversion methods to determine. Waveequationbased traveltime seismic tomography part 2. P, s, and surface waves can be used for tomographic models of different resolutions based on seismic wavelength, wave source distance, and the seismograph array coverage. Institute of physics publlshng journal of geophvsics and.
Detection of systematic errors in travel time data using a minimum 1d model. In fact, ray paths are determined by the calculation points or grid points located on the cell boundary thus. Seismic waveform inversion can provide a more detailed subsurface image than refraction travel time tomography or conventional velocity analysis yilmaz and clarbout, 1980. We change the model to minimize the difference between observed and computed travel times. For completeness, we begin our paper with a brief overview of the basic principles of travel time tomography. Zhu, land seismic imaging manager of conocophillips, was the first geophysicist who applied. Inversion of multichannel seismic data by combination of traveltime and fullwaveform tomography. A threelayer, feedforward artificial neural network was trained to perform a tomographic inversion of seismic travel time data for a simple 4 by 4 grid. Application of refraction seismic tomography method using. A numerical model was built according to the sites field. Pdf the jacobian matrix in the seismic traveltime tomographic equations usually contains several integral terms. In this study, a series of hydraulic tomography experiments were conducted at a porousfractured aquifer test site in goettingen, germany.
Local sources location and origin time part of the inversion. The travel time for highfrequency seismic waves is given by t i i 1 vxyz dx i sxyzd x 1 where vxyz is the velocity distribution, t i is the observed travel time. Seismic tomography is a technique for imaging the subsurface of the earth with seismic waves produced by earthquakes or explosions. Earth planets space, 57, 477489, 2005 recursive traveltime inversion. For example, with manual picking of phases, it is common. Seismic tomography i research school of earth sciences. Travel time tomography in travel time tomography we compare observed travel times against computed travel times. Pdf seismic travel time tomography in modeling low velocity. Tomographic inversion of seismic travel time data using. This method is based on the concept that the media, where the seismic waves prop. Waveequationbased traveltime seismic tomography part 1.
A tool for realtime seismic tomography masashi ogiso1. Detecting nearsurface objects with seismic traveltime tomography. In reflection tomography, sources and receivers are on the surface of the earth and the principal seismic events are reflections from subsurface velocity discontinuities. Bording march 2, 2006 1 introduction the word tomography. First, a linear relationship between the traveltime residual 1tdtobs tsyn and the relative velocity perturbation c. Initial model with positive anomaly, inversion result. The most common technique in the processing of 3d refraction data sets is the traveltime tomography. Ray tracing applied to travel time seismic tomography boll. The most important event related to the formation of the tocantins province is the collision between the amazonian and the sao francisco cratons and a third stable area, the paranapanema block hidden beneath the parana basin pimentel et al. Numerical examples all perform well with different seismic velocity models. The increasing topographic complexity and even use of a high curvature reflector in these models demonstrate the reliability. Frequencydependent traveltime tomography does not rely on the high. In this paper, we propose a waveequationbased traveltime seismic tomography method with a detailed description of its stepbystep process. Checkerboard resolution tests are conducted to verify the reliability of inversion results for the chosen seismic data and the waveequationbased travel time seismic tomography method.
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