Finding thickness of upper layer

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In summary, according to the information found in an aseismic experiment, the refracted P wave has a critical distance of 7.5 km and a critical time of 4.17 s. Therefore, the thickness of the upper layer is 1.8 meters.
  • #1
hopelesss
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My task is

Let's consider a model made up of two horizontal layers: the upper layer has a velocity
Vp1=3.0 km/s and the lower layer (or half space) has a velocity Vp2= 5.0 km/s. Aseismic experiment is conducted at the surface and showsthat the P wave refracted in the lower layer has a critical distance of 7.5 km and a critical time of 4.17 s. Based on this information, what is the thickness of the upper layer?

1. can i solve this by useing ti= (2z(v2^2 -v1^2)^1/2) / (v1*v2) and then
z= (ti*v1*v2) / 2(v2^2-v1^2)^1/2?
2. Is critical distance the thickness of layer 2?

greatful for any help
 
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  • #2
1. can i solve this by useing ti= (2z(v2^2 -v1^2)^1/2) / (v1*v2) and then
z= (ti*v1*v2) / 2(v2^2-v1^2)^1/2?
Check where the formula comes from, that should answer the question.
Where did the critical distance go there?

2. Is critical distance the thickness of layer 2?
No.
 
  • #3
It only say ''two-layer case with horizontal interface'' and the intercept time is given by ... and solving for refractor depth. And i can't find any equation with xcrit in it. tryed to google it but did not find any equation with Xcrit in it.
 
  • #4
Searching for "critical distance seismics" gives the Wikipedia article about seismic refraction as one of the first hits, and this article has a formula. I think it is hard to miss that.
 
  • #5
I only find seismic refraction when i google that.
I still don't get it. i would still miss the T0 if i use that equation. And the critical distance and critical time info would not have been used
 
  • #6
I think you don't need the critical time here.
 
  • #7
can i do this
ic= sin^-1 3/5 = 36,8
tan 36,8 = (7,5/2)/b = 0,75*3,75 = 2,8
And say upper layer is 2,8meters?
 
  • #8
Meters? Certainly not.

I don't understand what you calculated there (please add a sketch), in particular I don't see how this is supposed to include the path of the waves at the critical distance.
 
  • #10
This is not the critical distance.
 
  • #11
confused, taskes says ''Based on this information, what is the thickness of the upper layer?''
 

Related to Finding thickness of upper layer

1. How do you find the thickness of the upper layer?

To find the thickness of the upper layer, you can use a variety of methods such as drilling, seismic surveys, or ground-penetrating radar. These techniques involve measuring the depth of the upper layer from the surface of the earth.

2. What tools or equipment are needed to determine the thickness of the upper layer?

The tools and equipment needed will depend on the method being used. For drilling, you will need a drilling rig and drill bits. For seismic surveys, you will need a seismograph and geophones. For ground-penetrating radar, you will need a radar unit and antenna.

3. How accurate is the measurement of the thickness of the upper layer?

The accuracy of the measurement will also depend on the method being used. Generally, drilling can provide the most accurate measurement as it physically extracts a sample of the upper layer. Seismic surveys and ground-penetrating radar can also provide accurate measurements, but they may be affected by factors such as the type of material in the upper layer and the depth being measured.

4. Can the thickness of the upper layer vary in different locations?

Yes, the thickness of the upper layer can vary in different locations. This can be due to factors such as geological formations, soil types, and topography. It is important to take multiple measurements in different locations to get a more accurate understanding of the thickness of the upper layer.

5. How is the thickness of the upper layer used in scientific research?

The thickness of the upper layer is an important factor in many scientific studies, such as understanding the geological history of an area, predicting the potential for natural disasters, and determining the availability of resources. It is also used in engineering projects, such as building foundations and road construction, to ensure the stability and safety of structures.

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