Geophysics Forum

You certainly got a lot of new ideas. I will certainly read them when I got time. Currently I am so busy, but good to know there are some interesting ideas out there. I used to think seismology is almost dead: we already got the general idea, we just need to fill in the details.

You might be able to find a 2nd hand ground penetrating radar with that price range.

Anyone has Netflix subscription to share the thoughts about the documentary "Secrets of the Saqqara Tomb"?

Found an article about a GPR survey at Saqqara, don't know whether it's related.

https://www.tandfonline.com/doi/pdf/10. ... 20.1746891

Seismologists, like brave liars, lied, and continue to lie. You want to eat, so they lie! Earthquakes are impossible to predict! And to get a piece of the pie, you just need to declare to the whole earthly world that in 100 years, somewhere there will be an earthquake. This is how everyone can make...

I guess high resistivity zones correspond to fresh water bearing zones? And interestingly these zones have relative "flat" caliper readings. Maybe these zones are plugged?

I have done some geophysical borehole loggings before, but I am curious how you define plugging the water well. I guess if you plug the well only at the bottom, then you can still do the logging?

serguei58 wrote: ↑

Fri Jan 01, 2021 4:56 pm

Remember, earthquake prediction is impossible !!!

It depends on the definition of prediction. Long term earthquake predictions are apparently much better than short term predictions.

99thpercentile wrote: ↑

Fri Jan 01, 2021 4:20 pm

gopal123


Why did you retype my previous answer in your own words?

It looks like a spammer.

What do they do ERT survey for?

How deep was the tunnel? How big was it?

The link doesn't work -> file not found.

10KHz gives you better resolution and 3.5KHz gives you better penetration depth. I prefer 10Khz since clayey and silt sediments are more friendly than sands for penetration.

6pm in your local time? What's your time zone?

I took another look at the file. Now I realize it might be an underground wall with a slope. I think it's safe to say the mystery is mostly solved.

Kknq, please see a void model and its gpr data simulation below. You can see there are apparent different responses between the two sides and the middle of the void. When the void spacing (depth wise) is small, you can easily get the "ringing" effect as shown at the two sides due waves bouncing betw...

I still tend to believe it might be some kind of diffraction from something close to the ground surface, but it doesn't look like any diffractions I usually see. I haven't really think it through.

This is a GPR profile I collected close to a storm drain catch basin. The catch basin is at the ground surface between 13 to 16 ft in this profile. The strong "slope" signals to its left look very unusual. 270 MHz antenna.

Shielded or not, aboveground objects can show up in GPR data. GPR waves will be bounced back to the ground surface anyway -- they will keep travelling upward and then coming back down if there are aboveground objects.

To be honest, the anomalies do look like voids. I just realize that your tunnel might not be in a regular shape. I mean the top and walls of the tunnel might not be smooth at all. The GPR signals will bounce around inside the tunnel and show the signatures like the anomalies shown in your GPR profil...

At least you can see some anomalies. If the anomalies were caused by a tunnel, the tunnel might have collapsed. I think the more important question is, how large the area have you scanned. If you see this kind of anomalies everywhere, it's probably not a tunnel. If it's the only anomaly area you see...

If you drop a rock into a lake, the whole surface of the water becomes the wavefield as the water wave propagates. Each circle around the center where the wave starts is a wavefront. A wavefront is an interface (a straight line, a plane, a circle (as in this case)) or a ball, etc in the wavefield, o...