Search found 5 matches

by kd6iwd
Fri 31 Aug 2018 11:53
Forum: Cave Radio & Electronics
Topic: underground communication using seismic waves
Replies: 5
Views: 714

Re: underground communication using seismic waves

Here is a reference using 70-100 Hz to image a oil field at a depth of 3000' and the reflection of layers at 12,000' were measured all with frequencies higher than 40 Hz. See pages 55-58 in the following reference: https://www.slb.com/~/media/Files/resources/oilfield_review/ors95/aut95/08955260.pdf ...
by kd6iwd
Fri 31 Aug 2018 11:38
Forum: Cave Radio & Electronics
Topic: underground communication using seismic waves
Replies: 5
Views: 714

Re: underground communication using seismic waves

i just checked a page on sea floor mapping. The lowest frequency used for a ship towed array is 50 Hz. At that frequency depth penetration is in excess of 10,000 feet so in practical terms where the receiver is at depth rather than detecting a reflection, the depth penetration could easily be 10,000...
by kd6iwd
Thu 30 Aug 2018 10:08
Forum: Cave Radio & Electronics
Topic: underground communication using seismic waves
Replies: 5
Views: 714

Re: underground communication using seismic waves

A thought on a signal source, perhaps a electric solenoid could be used as a tapper controlled by the computer. There are many auto solenoids that could be used or you could roll your own. This might be a interesting approach fot generating a signal.

Best Regards

Jim
by kd6iwd
Thu 30 Aug 2018 09:28
Forum: Cave Radio & Electronics
Topic: underground communication using seismic waves
Replies: 5
Views: 714

Re: underground communication using seismic waves

The attenuation at seismic frequencies is quite low. The reflections from a 20,000 foot deep reflector are detected by a seismic sensor at the surface- so the signal had to transit 40,000 feet of rock to both get to 20,000 feet and then the weak reflection then returns to the surface. So, At seismic...
by kd6iwd
Fri 24 Aug 2018 19:22
Forum: Cave Radio & Electronics
Topic: underground communication using seismic waves
Replies: 5
Views: 714

underground communication using seismic waves

Dear sirs: I am a geologist and subscriber to the creg journal residing in the United States, and I have some thoughts on underground communication for your group that I would like to present. Cave communications have focused on radio which does indeed penetrate rocks however there is a alternative ...