https://www.enviro.wiki/index.php?action=history&feed=atom&title=Geophysical_MethodsGeophysical Methods - Revision history2026-04-15T01:13:54ZRevision history for this page on the wikiMediaWiki 1.31.1https://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=17865&oldid=prevJhurley at 21:06, 28 January 20262026-01-28T21:06:51Z<p></p>
<table class="diff diff-contentalign-left" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 21:06, 28 January 2026</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l56" >Line 56:</td>
<td colspan="2" class="diff-lineno">Line 56:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Forward Modeling===</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Forward Modeling===</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Forward (or synthetic) modeling (<del class="diffchange diffchange-inline">Fig. </del>4a) can be used to evaluate whether specific geophysical measurements are worthwhile at a given site. In this approach, the approximate size and physical property contrast between the target and background are estimated and used to generate synthetic datasets that represent the data that might be acquired in the field. These synthetic datasets can be corrupted with noise to better represent true field data, and then inverted to examine whether the target is likely to be detected with the proposed geophysical method. While forward modeling can never prove a geophysical method will be effective at a site, it can identify situations where that method will not be effective. Forward modeling should always be done prior to expending the time and expense of surface or cross borehole survey.<br /></div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Forward (or synthetic) modeling (<ins class="diffchange diffchange-inline">Figure </ins>4a) can be used to evaluate whether specific geophysical measurements are worthwhile at a given site. In this approach, the approximate size and physical property contrast between the target and background are estimated and used to generate synthetic datasets that represent the data that might be acquired in the field. These synthetic datasets can be corrupted with noise to better represent true field data, and then inverted to examine whether the target is likely to be detected with the proposed geophysical method. While forward modeling can never prove a geophysical method will be effective at a site, it can identify situations where that method will not be effective. Forward modeling should always be done prior to expending the time and expense of surface or cross borehole survey.<br /></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Parameter Estimation or ‘Inverse’ Modeling===</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Parameter Estimation or ‘Inverse’ Modeling===</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Parameter estimation or ‘inverse’ modeling (<del class="diffchange diffchange-inline">Fig. </del>4b) are used to estimate the spatial distribution of geophysical properties based on measurements at individual points. The most common inverse methods use an iterative approach where a mathematical model attempts to minimize the difference between the field measurements and the theoretical predictions based on a forward model for a synthetic model. Iterative parameter updates continue until these differences are less than the convergence criteria. At this point, the estimated model is a plausible representation of the physical structure of the subsurface. Unfortunately, geophysical inverse problems are usually under-determined, meaning there are many more model parameters than sensor observations. In this case, several different images or representations of the subsurface can match the field observations equally well. Additional model constraints are often included to favor certain models or images over others to narrow down the plausible possibilities further.  </div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Parameter estimation or ‘inverse’ modeling (<ins class="diffchange diffchange-inline">Figure </ins>4b) are used to estimate the spatial distribution of geophysical properties based on measurements at individual points. The most common inverse methods use an iterative approach where a mathematical model attempts to minimize the difference between the field measurements and the theoretical predictions based on a forward model for a synthetic model. Iterative parameter updates continue until these differences are less than the convergence criteria. At this point, the estimated model is a plausible representation of the physical structure of the subsurface. Unfortunately, geophysical inverse problems are usually under-determined, meaning there are many more model parameters than sensor observations. In this case, several different images or representations of the subsurface can match the field observations equally well. Additional model constraints are often included to favor certain models or images over others to narrow down the plausible possibilities further.  </div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>One of the most common constraints is called smooth inversion or smoothness constrained inversion because it produces models with smooth variations in physical properties. The result of a smoothness-constrained inversion is somewhat akin to looking at the earth with a very bad pair of glasses. The true structure appears ‘fuzzy’ and provides a low resolution glimpse into the structure of the earth (Fig. 4b)<ref>Day‐Lewis, F.D., Singha, K. and Binley, A.M., 2005. Applying petrophysical models to radar travel time and electrical resistivity tomograms: Resolution‐dependent limitations. Journal of Geophysical Research: Solid Earth, 110, B08206. [https://doi.org/10.1029/2004jb003569 doi:10.1029/2004JB003569]</ref>, which is a low-resolution approximation of the true subsurface structure (e.g., Fig. 4a). Site remediation professionals should be wary of high-resolution images with lots of structural detail. This structural detail may arise from an error in the inverse modeling. Reliable inverse modeling requires a trained user knowing how to correctly set up an inverse model and appropriately handle the data errors.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>One of the most common constraints is called smooth inversion or smoothness constrained inversion because it produces models with smooth variations in physical properties. The result of a smoothness-constrained inversion is somewhat akin to looking at the earth with a very bad pair of glasses. The true structure appears ‘fuzzy’ and provides a low resolution glimpse into the structure of the earth (Fig. 4b)<ref>Day‐Lewis, F.D., Singha, K. and Binley, A.M., 2005. Applying petrophysical models to radar travel time and electrical resistivity tomograms: Resolution‐dependent limitations. Journal of Geophysical Research: Solid Earth, 110, B08206. [https://doi.org/10.1029/2004jb003569 doi:10.1029/2004JB003569]</ref>, which is a low-resolution approximation of the true subsurface structure (e.g., Fig. 4a). Site remediation professionals should be wary of high-resolution images with lots of structural detail. This structural detail may arise from an error in the inverse modeling. Reliable inverse modeling requires a trained user knowing how to correctly set up an inverse model and appropriately handle the data errors.</div></td></tr>
</table>Jhurleyhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=15825&oldid=prevAdmin at 21:58, 26 April 20222022-04-26T21:58:33Z<p></p>
<table class="diff diff-contentalign-left" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #222; text-align: center;">Revision as of 21:58, 26 April 2022</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l7" >Line 7:</td>
<td colspan="2" class="diff-lineno">Line 7:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>'''<del class="diffchange diffchange-inline">CONTRIBUTOR</del>(<del class="diffchange diffchange-inline">S</del>):''' [[Dr. Lee Slater]]</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>'''<ins class="diffchange diffchange-inline">Contributor</ins>(<ins class="diffchange diffchange-inline">s</ins>):''' [[Dr. Lee Slater]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l85" >Line 85:</td>
<td colspan="2" class="diff-lineno">Line 85:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*[https://clu-in.org/characterization/technologies/geophysics/pages/decisionSupport.htm EPA Environmental Geophysics Decision Support System]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*[https://clu-in.org/characterization/technologies/geophysics/pages/decisionSupport.htm EPA Environmental Geophysics Decision Support System]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*[https://clu-in.org/characterization/technologies/geophysics/ EPA Geophysic Notice]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>*[https://clu-in.org/characterization/technologies/geophysics/ EPA Geophysic Notice]</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>*[https://<del class="diffchange diffchange-inline">youtu</del>.<del class="diffchange diffchange-inline">be</del>/HTukq9jDOzM USGS Fractured Rock Geophysical Toolbox Video]</div></td><td class='diff-marker'>+</td><td style="color: #222; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>*[https://<ins class="diffchange diffchange-inline">www</ins>.<ins class="diffchange diffchange-inline">youtube.com</ins>/<ins class="diffchange diffchange-inline">watch?v=</ins>HTukq9jDOzM USGS Fractured Rock Geophysical Toolbox Video]</div></td></tr>
</table>Adminhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=11438&oldid=prevAdmin: 1 revision imported2018-05-04T20:57:32Z<p>1 revision imported</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">Revision as of 20:57, 4 May 2018</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Adminhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=11122&oldid=prevAdmin: 1 revision imported2018-05-04T20:53:40Z<p>1 revision imported</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">Revision as of 20:53, 4 May 2018</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Adminhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=10842&oldid=prevAdmin: 1 revision imported2018-05-04T20:50:20Z<p>1 revision imported</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">Revision as of 20:50, 4 May 2018</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Adminhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=11437&oldid=prevAdmin: 1 revision imported2018-05-04T16:58:29Z<p>1 revision imported</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">Revision as of 16:58, 4 May 2018</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Adminhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=11121&oldid=prevAdmin: 1 revision imported2018-05-04T15:58:29Z<p>1 revision imported</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">Revision as of 15:58, 4 May 2018</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Adminhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=10841&oldid=prevAdmin: 1 revision imported2018-05-04T14:58:29Z<p>1 revision imported</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">Revision as of 14:58, 4 May 2018</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Adminhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=10513&oldid=prevAdmin: 1 revision imported2018-05-04T13:56:40Z<p>1 revision imported</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">Revision as of 13:56, 4 May 2018</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Adminhttps://www.enviro.wiki/index.php?title=Geophysical_Methods&diff=10233&oldid=prevAdmin: 1 revision imported2018-05-04T13:37:25Z<p>1 revision imported</p>
<table class="diff diff-contentalign-left" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #222; text-align: center;">Revision as of 13:37, 4 May 2018</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Admin