<div dir="ltr"><div class="gmail_default" style="font-family:monospace,monospace">Edward,<br><br></div><div class="gmail_default" style="font-family:monospace,monospace">Your recent inquiry to the USGS geomagnetism program was forwarded to me. We are currently transitioning to an email list-serve to help field questions about our operations and data products, so I hope you won't mind if I CC your question, and my response, to this server. If you want to continue this conversation, or think you may have reason to receive very occasional future emails related to our data products, you might consider registering yourself: <a href="https://geohazards.usgs.gov/mailman/listinfo/geomag-data">https://geohazards.usgs.gov/mailman/listinfo/geomag-data</a>.<br><br></div><div class="gmail_default" style="font-family:monospace,monospace">With that out of the way, here is my response to your inquiry (copied below):<br><br><div class="gmail_default" style="font-family:monospace,monospace">Short
answer: we don't have conductivity data available for the regions you
mentioned below; for reasons unknown they were not included
in the report from which these data were extracted (i.e., P. Fernberg
2012,
<a href="http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001026430" target="_blank">One-Dimensional
Earth Resistivity Models for Selected Areas of Continental United States and
Alaska</a>, EPRI Technical Update 1026430, Palo Alto, CA).<br><br></div><div class="gmail_default" style="font-family:monospace,monospace">Longer
answer: the data we *do* have are hypothetical 1-D models of
conductivity constructed from geological/geophysical research articles
published in the past. They are organized by physiographic provinces
that only roughly approximate the geographic bounds of conductivity
("physiographic" pertaining to surface features, *not* the actual
underlying geology). Some of the depth-dependent conductivities are
measured (e.g., using magnetotelluric or magnetic sounding techniques),
but most are estimated from knowledge of the underlying geology, and
laboratory measurements of the conductivity of similar rock types. These
1-D conductivities, with large uncertainty bounds, should be considered
representative of their region, and not necessarily accurate for any
particular location. For this reason, it is not unreasonable to choose a
nearby region that *does* have conductivity data to serve as a proxy
for a region where it is missing, especially if there is reason to
believe the two regions have similar underlying geology.<br><br></div>Long-term
plans: We are working to convert magnetotelluric
measurements made in the United States' NSF Earthscope program into a self-consistent, and
much more physically realistic, 3-D model of conductivity. There is no
firm delivery date for this, but it is probably safe to say it will go public within a 1-2 year time frame, with beta releases somewhat earlier, and
regular updates following on. <br><br></div><div class="gmail_default" style="font-family:monospace,monospace">Thanks for your interest in the USGS Geomagnetism Program.<br><br></div><div class="gmail_default" style="font-family:monospace,monospace">Kind Regards,<br></div><div class="gmail_default" style="font-family:monospace,monospace">Josh Rigler<br><br></div><div class="gmail_default" style="font-family:monospace,monospace"><br>---------- Forwarded message ----------<br>From: <b class="gmail_sendername">Edward Oughton</b> <span dir="ltr"><<a href="mailto:e.oughton@jbs.cam.ac.uk" target="_blank">e.oughton@jbs.cam.ac.uk</a>></span><br>Date: Sun, Feb 21, 2016 at 10:41 AM<br>Subject: Regional Resistivity<br>To: "<a href="mailto:geomagdata@usgs.gov" target="_blank">geomagdata@usgs.gov</a>" <<a href="mailto:geomagdata@usgs.gov" target="_blank">geomagdata@usgs.gov</a>><br><br><br>
<p class="MsoNormal"><span style="font-size:12pt;font-family:"Times New Roman",serif">Dear Sir/Madam,<br>
<br>
I noticed a couple of regional gaps in this data with no model being assigned. This includes:</span></p>
<ul type="disc"><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Northern Rocky Mountains</span></li><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Middle Rocky Mountains</span></li><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Wyoming Basin</span></li><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Southern Rocky Mountains</span></li><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Ozark Plateaus</span></li><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Ouachita</span></li><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Interior low plateaus</span></li><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Eastern Maryland, Delaware and New Jersey</span></li><li class="MsoNormal">
<span style="font-size:12pt;font-family:"Times New Roman",serif">Northwest Massachusetts, Vermont, New Hampshire and Northern Maine</span></li></ul>
<p class="MsoNormal"><span style="font-size:12pt;font-family:"Times New Roman",serif">Is this because we don't have data available for these locations, or do they serve some sort of baseline?
<br>
<br>
Any help would be very much appreciated. <br>
<br>
Thanks and best wishes,<br>
<br>
<br>
</span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Courier New"">Edward</span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Courier New""> </span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Courier New"">--
</span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Courier New"">Dr Edward J. Oughton
</span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Courier New"">Senior Risk Researcher</span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Courier New"">Centre for Risk Studies</span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Courier New"">Judge Business School</span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Courier New"">University of Cambridge</span></p>
<span style="font-size:10pt;font-family:"Courier New"">T: +44 (0) 7920 401 571</span><br></div><div class="gmail_default" style="font-family:monospace,monospace"><br><br clear="all"></div><br>-- <br><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><span style="font-family:monospace,monospace">E. Joshua Rigler<br></span></div><div><span style="font-family:monospace,monospace">Research Geophysicist<br></span></div><div><span style="font-family:monospace,monospace">Geomagnetism Program</span></div><div><div><span style="font-family:monospace,monospace">U.S. Geological Survey</span></div></div></div></div></div></div>
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