Great post George and he is correct, geophysics isn't cheap or easy. For those that are interested in seeing many of the different geophysical techniques demonstrated, you can attend the 6th Texas Hydro Geo Workshop to be held at Cave Without a Name in Boerne, Texas. Dates are Friday, October 4 through Sunday, October 6. You can register on line at https://hydrogeoworkshop.org/ and also review last year's program to get an idea of what is offered. The workshop is set up with a series of approximately 40 modules on various forms of field data collection and interpretation. We usually have more than 300 people attend the workshop from across the state and surrounding states.
In past years we've had experts in the field demonstrating Electrical Resistivity, Ground Penetrating Radar, and Natural Potential in addition to numerous borehole geophysical techniques. Other modules include stream gauging, water sample collection, field safety, introduction to caving, rock identification, aquatic biology, karst feature identification, tracer testing, cave geology, environmental drilling, and core analysis, etc. Thanks, Geary Schindel Co-Chair Texas Hydro Geo Workshop From: Texascavers <texascavers-boun...@texascavers.com> On Behalf Of George Veni Sent: Saturday, August 3, 2019 12:59 AM To: texascavers@texascavers.com Subject: Re: [Texascavers] MOPAC extension meets "karst features" Microgravity is a great technique, but like everything has its pros and cons. The units themselves run in the $70,000-$90,000 range, depending on the model. Unlike resistivity and some other methods that give you measurements throughout the slice of earth you are studying, microgravity gives data for each point measured, which is then interpolated for the areas in between. If you're looking for typical meter-diameter or smaller karst features found in the MOPAC area, you're talking about making measurements every meter if you want to maximize the chances of finding them. So if you're looking only at a 100 m x 100 m area, and measuring a 1-m grid, that's 10,000 individual measurements. If the technician making the measurements is good and very fast, you're looking at best at 1 measurement every 10 minutes, which totals nearly 17,000 hours, which at a typical consulting rate for a technician of $50/hour that's $85,000 just for the field work, which doesn't include data entry, processing, analysis, etc. to get the actual usable results--and the folks who will do that will charge substantially more. I forgot to mention in my previous message that with geophysics you also often have to trade depth of study for the level of detail. Usually, if you are looking for small features you can't see deeply. If you look deep, you usually aren't seeing small features, only big ones. Sometimes two surveys are done by the same technique of the same area, one to look shallowly and one deeply. To complicate matters further and add to the costs, all geophysical techniques have strengthens and weaknesses. I usually like to use microgravity and electrical resistivity together because they complement each other nicely. Where each is weak, the other is strong, so if you get a hit on both you have much higher confidence in your interpretation and in avoiding false positives and negatives. No matter what system you choose, high costs and technical complications and limitations will keep the effort from being easy or cheap. George (Sent from my mobile phone) ******************** George Veni, PhD Executive Director, National Cave and Karst Research Institute (NCKRI) and President, International Union of Speleology (UIS) NCKRI address (primary) 400-1 Cascades Avenue Carlsbad, New Mexico 88220 USA Office: +575-887-5517 Mobile: +210-863-5919 Fax: +575-887-5523 gv...@nckri.org<mailto:gv...@nckri.org> www.nckri.org<http://www.nckri.org> UIS address Titov trg 2 Postojna, 6230 Slovenia ***This is an external email - beware links & attachments from unknown senders***
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