Search found 149 matches

by Preston09
Thu Jul 09, 2015 8:20 am
Forum: General Geophysics
Topic: Mechanical Engineer interested in Geophysics
Replies: 12
Views: 1933

Re: Mechanical Engineer interested in Geophysics

I don't see there is a close relationship between mechanical engineering and geophysics but it doesn't prevent you to go for a master degree in geophysics. I think either physics or computer is fine as a minor for geophysics. You actually need both in geophysics. Physics helps you to understand the ...
by Preston09
Thu Jul 09, 2015 8:09 am
Forum: Oil and Gas Exploration
Topic: What is 'seismic wavelet'?
Replies: 2
Views: 661

Re: What is 'seismic wavelet'?

From my understanding, a wavelet could represent the source wave. In another word, it represents the initial input to a system. Typically it is a spike signal with a very short period generated by sources such as explosives and water guns, etc. The convolution of the input and the system parameters ...
by Preston09
Thu Jun 04, 2015 10:11 am
Forum: Near Surface Geophysics
Topic: checker-board test
Replies: 7
Views: 924

Re: checker-board test

Apparently you need a software which can do both inversion and forward modeling. I never used it, but you can try Reflexw: http://www.sandmeier-geo.de/refraction_seismics.html For sensitivity testing using the software or any other similar ones, you basically have to setup models to to do forward mo...
by Preston09
Thu Apr 02, 2015 12:26 pm
Forum: Oil and Gas Exploration
Topic: Safe Seismic Testing Devices Introduced in Midland Neighborhoods (Video)
Replies: 1
Views: 416

Re: Safe Seismic Testing Devices Introduced in Midland Neighborhoods (Video)

The device has a lot of cables, not like a simple geophone. I guess each one of them is a small seismograph?
by Preston09
Tue Mar 24, 2015 2:46 pm
Forum: Near Surface Geophysics
Topic: 3D seismic tomography
Replies: 10
Views: 2177

Re: 3D seismic tomography

I use SeisImager, but you can also try seisOpt® @2D™ or zondst2d. Check this thread:
viewtopic.php?f=2&t=1817
by Preston09
Tue Mar 24, 2015 1:50 pm
Forum: Near Surface Geophysics
Topic: 3D seismic tomography
Replies: 10
Views: 2177

Re: 3D seismic tomography

Do 2d seismic refraction tomography and combine the results from 2d into 3d. This is how I would do it.
by Preston09
Fri Mar 06, 2015 3:36 pm
Forum: Near Surface Geophysics
Topic: Merging seismic record files
Replies: 2
Views: 476

Re: Merging seismic record files

It's an easy task to merge files. The software you are going to use to process the data should have this feature. I use Pickwin (SeisImager).
by Preston09
Fri Mar 06, 2015 3:27 pm
Forum: Near Surface Geophysics
Topic: 3D MASW Field Setup
Replies: 4
Views: 716

Re: 3D MASW Field Setup

You should use 4.5Hz geophones if you want good results on deeper depths using MASW. 14Hz is not good enough for 20m depth.
by Preston09
Sun Mar 01, 2015 1:24 pm
Forum: Near Surface Geophysics
Topic: 3D MASW Field Setup
Replies: 4
Views: 716

Re: 3D MASW Field Setup

Hello all, I am intending to do a 3D MASW survey to investigate some shallow fractures (max. 30 m depth), could anybody please tell me what is the field procedure and field setup for a 3D MASW?? Thank you very much. I don't think there are really 3D MASW surveys, but you can construct 3D images usi...
by Preston09
Thu Sep 11, 2014 1:07 pm
Forum: Near Surface Geophysics
Topic: US Alliance weight drops systems
Replies: 8
Views: 1064

Re: US Alliance weight drops systems

Technically the main disadvantage of MASW is the horizontal resolution, but currently the main problem is that the engineers are used to refraction method and not familiar with the idea of MASW. Old habits are hard to change. :(
by Preston09
Wed Sep 03, 2014 11:34 am
Forum: Near Surface Geophysics
Topic: US Alliance weight drops systems
Replies: 8
Views: 1064

Re: US Alliance weight drops systems

I never used this system, but a weight drop system should be the choice for the spread length you mentioned. If you look for less expensive P wave source, you can try this: http://www.rtclark.com/PAGE/New_Product ... -40kg.html
by Preston09
Tue Aug 26, 2014 6:05 pm
Forum: General Geophysics
Topic: 3D DIPPING LAYER
Replies: 1
Views: 556

Re: 3D DIPPING LAYER

What's so special about 3D? I don't see the difference between 2D and 3D if there is just one seismic refraction profile.
by Preston09
Thu Jul 24, 2014 5:03 pm
Forum: Oil and Gas Exploration
Topic: error: subcalls.c: efopen: fopen failed
Replies: 10
Views: 1579

Re: error: subcalls.c: efopen: fopen failed

Check your data file and see whether it's valid.
by Preston09
Wed Jun 18, 2014 3:47 pm
Forum: General Geophysics
Topic: Best technique for filtering accelerometer data?
Replies: 15
Views: 1626

Re: Best technique for filtering accelerometer data?

Vertical geophones would be just fine. I suppose they are cheaper.
by Preston09
Tue Jun 17, 2014 3:31 pm
Forum: General Geophysics
Topic: Best technique for filtering accelerometer data?
Replies: 15
Views: 1626

Re: Best technique for filtering accelerometer data?

Kbkofoed wrote:https://www.sparkfun.com/products/11744 ... c6398b456a

Would this geophone do the trick?
It looks like a good one although a standard 4.5Hz geophone could be better. You can surely give it a try.
by Preston09
Mon Jun 16, 2014 9:15 pm
Forum: General Geophysics
Topic: Best technique for filtering accelerometer data?
Replies: 15
Views: 1626

Re: Best technique for filtering accelerometer data?

You can try oscillation frequency or natural frequency, but I doubt you can find something better than geophones.
by Preston09
Sun Jun 15, 2014 8:22 pm
Forum: General Geophysics
Topic: Best technique for filtering accelerometer data?
Replies: 15
Views: 1626

Re: Best technique for filtering accelerometer data?

The better way to decide where the wave come from is to use multiple sensors as in earthquake monitoring. For example, you can arrange 3 geophones in a triangle shape, then use their arrival-time differences to determine the origin. You won't get useful data using the accelerometer with its resonant...
by Preston09
Sun Jun 15, 2014 3:13 pm
Forum: General Geophysics
Topic: Best technique for filtering accelerometer data?
Replies: 15
Views: 1626

Re: Best technique for filtering accelerometer data?

What's the resonant frequency of the accelerometer? We typically use geophones with resonant frequency of a few Hz. If the resonant frequency of the accelerometer is in the range of KHz, it is not suitable for this type of tests.
by Preston09
Sun Jun 15, 2014 9:37 am
Forum: General Geophysics
Topic: Best technique for filtering accelerometer data?
Replies: 15
Views: 1626

Re: Best technique for filtering accelerometer data?

Are you testing it in a sandy-soil environment? Seismic waves don't travel far in beach sands. Where did the noises come from?
by Preston09
Fri May 30, 2014 11:12 am
Forum: General Geophysics
Topic: how to use memmapfile of MATLAB?
Replies: 4
Views: 1318

Re: how to use memmapfile of MATLAB?

I think you missed the trace header which should be 240 bytes before the trace data.
by Preston09
Tue May 20, 2014 4:47 pm
Forum: General Geophysics
Topic: 2D HR Marine Seismic Reflection Processing by Using SU
Replies: 3
Views: 1295

Re: 2D HR Marine Seismic Reflection Processing by Using SU

This is a lot of work. Thanks for sharing! I think it's great to show your work - it can be really useful for others who are trying to do similar practices.
by Preston09
Thu May 15, 2014 6:39 am
Forum: Near Surface Geophysics
Topic: Seismic source in a rather unusual environment
Replies: 6
Views: 851

Re: Seismic source in a rather unusual environment

You use a plate for the hammer, right? A rubber plate on top of a steel plate might be helpful to generate stronger low frequency signals. It might be helpful to use a pipe with one end sealed with a plate. Hammer the plate from inside the pipe to push the plate againist the soils until it reach rel...
by Preston09
Wed May 14, 2014 6:26 pm
Forum: Near Surface Geophysics
Topic: Seismic source in a rather unusual environment
Replies: 6
Views: 851

Re: Seismic source in a rather unusual environment

You can use a hydraulic hammer.
by Preston09
Wed Feb 19, 2014 10:59 pm
Forum: Buy, Sell or Trade
Topic: RADEXPRO Seismic Processing Package
Replies: 1
Views: 1023

Re: RADEXPRO Seismic Processing Package

Nobody has placed a bid yet? Hmm...
by Preston09
Sun Feb 09, 2014 6:49 pm
Forum: Near Surface Geophysics
Topic: 1.5 km seismic refraction line
Replies: 10
Views: 1098

Re: 1.5 km seismic refraction line

You probably need permit to use explosives, you'd better contact local authorities/experts with that.