Questions tagged [seismology]

For questions about the study of earthquakes and various seismic sources.

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11
votes
2answers
652 views

Is it possible to prevent high magnitude earthquakes by induced earthquakes?

As we know, earthquakes can be induced by human activities. Can we induce earthquakes around faults regularly so that the energy releases regularly, and hence prevent high magnitude earthquakes by ...
4
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1answer
677 views

Are volcanoes formed from earthquakes?

I know that some earthquakes are caused by volcanoes and that some earthquakes can trigger volcanic eruptions close to where the earthquake is. But what if a great earthquake(8.0 or above) occurs and ...
20
votes
4answers
2k views

What would a replacement for SEGY look like?

I have been having a miserable time this week reading SEGY files. This is data from the largest seismic acquisition company in the world whose client is the 7th largest oil company in the world. So if ...
3
votes
1answer
148 views

Which component in a 3-component Sp receiver function is the actual Sp RF?

In a 3-component Sp RF I have the green's function in P,SV, and SH. The actual component to the RF that shows the Sp conversion (the one always published in the literature), which would represent as a ...
7
votes
1answer
198 views

Should RTM amplitudes (pre- and post-stack) be related to rock physics properties?

There is as huge uplift in the image quality near and under salt bodies (e.g. the Middle Miocene of the deepwater Gulf of Mexico) by using reverse time migration or RTM. We can now make accurate ...
6
votes
1answer
452 views

How are the ZNE, ZRT and LQT coordinate systems defined?

I'm confused about the direction of Z (upward or downward?), R (outward or toward the source?) and T.
7
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1answer
257 views

Will another big earthquake hit Kathmandu?

Recently, we got the news that the western part of Nepal may be hit by a larger earthquake than that of April 25, because it did release all of its energy. During the earthquake, only the eastern part ...
5
votes
2answers
2k views

What would change if our earth lacks mountains?

I just asked myself what is the role of the mountains on our planet earth? Well there's a well known role for the climate and weather. But is there a kind of physical or geological role? What would ...
17
votes
2answers
377 views

How strong can a glacial icequake get?

While researching Antarctic geology, I came across the term 'icequake' in the abstract to the article Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ...
8
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1answer
127 views

Evidence of a seismic trigger of the Storegga Slide ~8.2ka

The Storegga Slide was a catastrophic underwater landslide that occurred off the coast of Norway about 8,200 years ago. This YouTube clip shows simulations that indicate that this slide resulted in ...
7
votes
0answers
322 views

What geological structure(s) is responsible for the recent Queensland earthquakes?

Recently, south-east Queensland has been rattled by 2 moderate earthquakes - a 5.3 a couple of days ago (News report) and a 5.7 tremor just a few hours ago as of writing this post (News Report). These ...
6
votes
1answer
439 views

Why is it necessary in seismic imaging to calculate an image of reflection coefficients when one of the inputs is the velocity model?

Note: I'm not at all an expert in this field. I read in the first few pages of Robein (2010; Seismic Imaging, A Review of the Techniques, their Principles, Merits and Limitations, EAGE) that both ...
7
votes
1answer
82 views

Publicly-available real-time world-wide seismographic information?

Is there a list of websites supplying real time seismographic information for around the world? I could find for specific places. But I'm looking for a list so I can check for anywhere (providing, of ...
6
votes
1answer
104 views

Querying Seismic Databases

I'm trying to find 3-component records of the P-wave arrivals of a variety of earthquakes at seismic stations (specific earthquakes or stations aren't important, I just want a small library of these ...
14
votes
2answers
581 views

Why is a seismogram interpreted as a convolution?

I remember reading in a geology book that a seismogram is a convolution between a source signal and propagation effects. In layman's terms, what does this really mean?
7
votes
1answer
2k views

What is the meaning of seismic spectral blueing?

What is the meaning of seismic spectral blueing? Please cite any good introductory materials if possible.
12
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4answers
1k views

What do the derivative or the integral of amplitude of a seismogram mean?

I'm doing a project in which I'm analyzing earthquake seismogram waves. I used a program to graph the exact amplitudes and how they changed over the course of a single earthquake. For the project I ...
10
votes
1answer
2k views

How does one determine the optimum offset in a seismic survey?

I was going through a report on MASW (Multi Station Analysis of Surface Wave) and found this "To avoid the aliasing in the space domain, geophone spacing (Δx) needs to be less than half of the ...
12
votes
1answer
2k views

Should one extract wavelet from seismic or well log for the generation of synthetic traces?

Synthetics are generated by convolving reflectivity series with the known wavelet. I have seen most of the wavelet are extracted from seismic data itself. Is there any hard and fast rule, or can one ...
9
votes
1answer
87 views

Groundwater unloading and corresponding changes in fault zone stick-slip behavior

I was intrigued by this Slate piece, more or less a summary of Amos et al. (2014)'s Nature article, which essentially states that groundwater depletion and subsequent crustal unloading causes a ...
14
votes
0answers
150 views

What are the ground motion prediction equations for 3-D ruptures?

Ground motion prediction equations (GMPEs) estimate ground motion at any given site due to an earthquake at a distance. There are many such equations, each with different parameters. Can somebody ...
7
votes
1answer
679 views

Why do most seismic inversion methods ignore high frequencies?

Different post-stack inversion methods such as model based, sparse spike, colored and recursive inversion methods use high cut frequency impedance logs (low frequency) and mid-frequency seismic trace ...
7
votes
1answer
1k views

Why does part of the P-wave convert into a S-wave with an increase of incidence angle?

With the increase of incidence angle, a portion of a P-wave converts into a S-wave, how does this behaviour occur?
3
votes
1answer
422 views

How to determine the number of bytes in the SEGD Revision 1 interblock gap

How can one determine the number of bytes in the SEGD Revision1 interblock gap? The quantity is present on page 5 of the standards document.
22
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1answer
132 views

Placement of crustal thickness estimation from 1D inversion of surface wave dispersion curves

Seismic surface waves present a characteristic dispersion behavior in which different frequencies travel at different speeds. This characteristic dispersion curve depends on the shear and ...
8
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2answers
2k views

Distance to epicenter vs distance to focus

I am not really a "budding seismologist." I am a chemistry/physics teacher teaching an Earth science class (low academic level) in a small-town high school. (My college coursework in earth sciences = ...
12
votes
1answer
2k views

converting SU file to ASCII format in seismic unix using OpenSeaSeis

I have tried to convert a Seismic SU file to ASCII format in seismic unix using openseaseis module named "sutoascii". I have already tested the SU file by opening it in SeaView Seismic Viewer and ...
18
votes
2answers
2k views

Why Vp/Vs and not Vs/Vp?

The relation between shear wave velocity (Vs) and pressure wave velocity (Vp) is often expressed as Vp/Vs. Wouldn't the opposite be more logic? Vs/Vp would never lead to division with zero and the ...
6
votes
1answer
414 views

Earthquake probabilities

A recent report estimated the probability of an earthquake greater than magnitude 7 on the southern section of the San Andreas fault at approximately 60% over the next thirty years. How is that ...
8
votes
1answer
2k views

Calculating the displacement of a fault

In the calculation of scalar moment magnitude of an earthquake we have the formula $$M_0=\mu AD$$ where: $\mu$ is the shear modulus of the rocks involved in the earthquake (in Pa) $A$ is the area ...
8
votes
1answer
241 views

About Earthquakes and their properties

I know this sounds like a crazy observation but San Francisco has a lot of HUGE buildings in the downtown area , millions of tons or probably more. Many Scientists think a big earthquake there is '...
11
votes
1answer
163 views

What efforts have been made to separate the microseismic events related to wind-related ocean waves from the components of volcanic origin?

I have read the question What generates the microseism? and it's accompanying answer. In [#1, cited below], they use the azimuth values of seismographic activity on the flanks of the volcano ...
12
votes
2answers
1k views

Temporal Resolution of Seismic data

Radius of the Fresnel zone is given by $$Rf=(v/2)(t_0/f_\mathrm{dom})^{1/2}$$ where $v$: velocity of layer $t_0$: two way travel time $f_\mathrm{dom}$ :dominant frequency in the spectrum This shows ...
14
votes
1answer
186 views

How are Richter magnitudes of past earthquakes estimated?

In reading about historical major earthquakes, in particular, the Great Shaanxi Earthquake that killed approximately 830,000 people in July, 1556, there is a claim made about the approximate Richter ...
17
votes
1answer
401 views

Can earthquakes contribute to Antarctic ice loss?

I read about the earthquake that took place in Japan in 2011, led to some small calving events in Antarctica (link). So, it makes me think if there is a big earthquake near or in Antarctica, can it ...
12
votes
1answer
205 views

Why does seismic activity shed light on the inner core rigidity?

Reading Introduction to Geology (MIT 2005) and Wikipedia's article on Earth's inner core, it is specified that: Earth was discovered to have a solid inner core distinct from its liquid outer ...
12
votes
1answer
230 views

Do normal modes of oscillation cause permanent deformation?

It is known that when a large earthquake occurs, say $M \ge 9.0$, The surface waves travel around Earth over and over, "ringing the surface like a bell". The GIF below is an example (Image Source): ...
13
votes
1answer
698 views

Successful Earthquake predictions

Have there been any instances where seismologists have successfully predicted the occurrence of earthquakes? If so, then why has the number of scientists working on this area has declined (as ...
13
votes
1answer
354 views

How much silicon is in the Earth's core, and how did it get there?

With some informal conversation with a peer of mine, he had suggested that there is evidence (which he couldn't find,but had remembered reading) that there was Silicon in the Earth's core. I referred ...
12
votes
1answer
639 views

What causes “shallow” moonquakes?

It is thought that "deep" moonquakes are caused by tidal forces exerted on the Moon by the Earth and Sun. Some other sorts of moonquakes are thought to be caused by impacts, or by thermal expansion (...
9
votes
1answer
142 views

What are the factors that dictate a given topology for seismometer placement around a volcano?

The image below (borrowed from [#1]) shows the topology of the seismometers around the volcano Stromboli. In the text, they explain the following: The seimometers were set on the flanks of the ...
11
votes
1answer
340 views

How accurately can explosions be triangulated from the IRIS seismogram data?

There's a bunch of armed conflicts going on right now. What are the lower boundaries on accuracy of triangulating and timing man-made events from the IRIS datasets (accessible, for instance, with the ...
15
votes
1answer
1k views

Interpretation of a seismogram (three components)

In most cases (as shown in the figure below), a seismogram shows data from three components: North-South East-West Vertical/depth(z) However, if these components are not marked and all we have are ...
11
votes
1answer
321 views

Relation between fault rupture aspect ratio and slip rate?

I am modeling a fault surface (which I consider to be a plane rectangle). I got the area of the surface, but the orientation is unknown, which can be found out if the aspect ratio of the rectangle is ...
13
votes
1answer
216 views

Epicenter location of the 900-930 A.D.,7.4 Magnitude Seattle Earthquake?

I am preparing a seismic hazard map of Seattle and I was curious about the great 7.4 magnitude earthquake that occurred in the Seattle area during 900-930 A.D. On a second note, is it possible to ...
12
votes
1answer
200 views

Probability distribution of fault throw displacement and height limiting mechanisms

First, what is the probability distribution of fault throw displacement. Uniform distribution seems unlikely, since then small changes would add up to huge huge elevation differences that require a ...
13
votes
1answer
6k views

P wave to S wave conversion

While passing through layers inside the earth some P waves get converted to S waves and then back to P waves while returning towards the surface. Is this statement true? If yes, then why? (...
17
votes
3answers
552 views

Are there any techniques for imaging the deep Earth besides seismic waves?

It is well-known that we can learn a lot about the structure of the lower crust, mantle, and core by observing the ways in which they refract different kinds of seismic waves. Do we have any other ...
12
votes
2answers
4k views

Why is colored seismic inversion called 'colored'?

One of the seismic inversion algorithms is called 'colored' inversion. It is performed in the frequency domain and the point is in building an operator that directly transforms a seismic trace into ...
12
votes
1answer
2k views

Is there any correlation between La Niña/El Niño and seismic activity?

I've read in the past that extreme precipitation levels may have an effect on seismic activity, and wondered if anyone has ever analysed the La Niña / El Niño cycles to see if there are any ...