• Login
    View Item 
    •   Home
    • Theses & Dissertations
    • 2014 - Mines Theses & Dissertations
    • View Item
    •   Home
    • Theses & Dissertations
    • 2014 - Mines Theses & Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Mines RepositoryCommunitiesPublication DateAuthorsTitlesSubjectsThis CollectionPublication DateAuthorsTitlesSubjects

    My Account

    Login

    Mines Links

    Arthur Lakes LibraryColorado School of Mines

    Statistics

    Display Statistics

    Improved temporal and spatial focusing using deconvolution: theoretical, numerical and experimental studies

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Douma_mines_0052N_10453.pdf
    Size:
    8.193Mb
    Format:
    PDF
    Description:
    Improved temporal and spatial ...
    Download
    Author
    Douma, Johannes
    Advisor
    Snieder, Roel, 1958-
    Date issued
    2014
    Date submitted
    2014
    Keywords
    time reversal
    microseismic
    focusing
    deconvolution
    Time reversal
    Seismic reflection method -- Deconvolution
    Seismic waves
    Microseisms
    Green's functions
    
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11124/445
    Abstract
    Time Reversal can be used to time reverse and propagate the measured scattered waveforms to a point in both time and space, ideally to a delta function [delta(r with an arrow over it)delta(t)]. This is commonly referred to as time reversal focusing and has led to time reversal being applied in a wide variety of fields such as medicine, communications, nondestructive evaluation (NDE), and seismology. In practice, time reversal is not optimal for generating a delta function focus if certain conditions are not upheld. For time reversal to work perfectly, the following four conditions must be present: (1) one must record for an infinitely long period of time; (2) Green's functions must be assumed to contain infinite bandwidth; (3) attenuation must be absent within the medium; and (4) one must have full coverage of the wavefield. Due to the need for these conditions, much research is being carried out in order to enhance the time reversal process in practice. We introduce deconvolution, a simple and robust approach, in order to calculate an optimal signal for back propagation designed to give an improved focus. We demonstrate experimentally that deconvolution is able to dramatically improve the temporal focus compared to time reversal. Through a joint project with Los Alamos National Laboratory, we compared time reversal to deconvolution. The results showed that deconvolution was able to dramatically improve the temporal focus for a source and a receiver which were both located on the surface of our object. We then continued our experimental studies of deconvolution by doing a joint project with researcher Dr. Ernst Niederleithinger from the Federal Institute for Materials Research and Testing (BAM). For this experiment, we placed multiple sources within a concrete block and recorded the source wavefields on the surface with a single receiver. This experiment was designed to further test the robust nature of deconvolution and compare its temporal focusing capability to that of time reversal. All of these experimental studies show that deconvolution was able to improve the temporal focus compared to time reversal. We continued our comparison study between time reversal and deconvolution and demonstrated theoretically, experimentally, and numerically that deconvolution also improves spatial focusing. We give a proof explaining why one would expect improved spatial focusing when there is improved temporal focusing for both a acoustic and elastic media. We then demonstrate in our experiments the improved spatial focus achieved using deconvolution by scanning around the source location with a laser vibrometer at the time of focus for an acoustic case. Finally, we use deconvolution to locate synthetic microseismic events to prove numerically that improved temporal focusing leads to improved spatial focusing for both acoustic and elastic media.
    Rights
    Copyright of the original work is retained by the author.
    Collections
    2014 - Mines Theses & Dissertations

    entitlement

     
    DSpace software (copyright © 2002 - 2023)  DuraSpace
    Quick Guide | Contact Us
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.