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# Questions tagged [seismology]

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

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236 views

### Carbonate reef not horizontal in seismic section?

Carbonate reefs usually appear as homogeneous bodies surrounded by sediment layers in seismic reflection data, but in the figure below the high amplitude reflection from the top of sediment (layer 2 ...
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 ...
139 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 ...
105 views

Is it possible for an earthquake to generate such a design in a sand pendulum during an earthquake? I saw an article online describing the story of a shop owner finding one of his pendulums had ...
85 views

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 ...
303 views

### Is seismology really the only way to measure the thickness of Earth's layers?

Answers from these two questions: How can we guess the size of the earths inner core? & How can we measure the thickness of the earths mantle? use seismic waves as the method for detirmining ...
137 views

### Regarding velocity of P/S-waves

I feel like I am missing something blindingly simple, but I am curious about something. We are given the velocity of a P-wave as $v_{p} = \sqrt{(K+\frac{4}{3}μ)/ρ}$. So I am to understand ...
125 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 ...
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 ...
261 views

### Can a 99.9% probability of an M≥ 5 earthquake within a 3-year period be verified?

Paper: Potential for a large earthquake near Los Angeles inferred from the 2014 La Habra earthquake (2015) Obviously there has been much discussion on the viability of earthquake prediction. This ...
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 = ...
125 views

### Earthquakes in Oklahoma influenced by Humans?

I'm currently living in Oklahoma, and there has been an abnormal amount of earthquakes lately, by abnormal I mean more then 5 in a day(not sure if that's normal or not).. I've also been told that in ...
642 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 ...
753 views

### Where does the 2015 Nepal earthquake rank amongst earthquakes since 1900?

Wikipedia provides a list of deadly earthquakes since 1900. Where would the April 2015 Nepal earthquake (magnitude currently estimated as 7.8 or 8.1) rank in this list, in terms of magnitude?
191 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 ...
235 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 '...
289 views

### How to interpret seismic interferometry data?

Here is a screenshot of coseismic interferometry measurements of the 2015 Nepal earthquake. What does it mean? The star is the epicenter of the earthquake. The screenshot was taken from the UNOSAT ...
178 views

### Prompt gravity signal induced by the 2011 Tohoku-Oki earthquake - could this really be useful for warnings?

Edit: Two new items may shed more light on this question: BBC: Gravity signals rapidly show true size of giant quakes links to: Science: Observations and modeling of the elastogravity signals ...
158 views

### How do they know the 2016 Kaikoura (NZ) Earthquake was 'complex', involved six different faults?

The BBC news article New Zealand quake: The geological impact of a 'complex' tremor says: The powerful earthquakes which hit New Zealand were some of the most complex ever recorded, say scientists. ...
250 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 ...
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.
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 ...
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?
562 views

### Analytical solution for seismic wavefield in MATLAB

I have been trying to evaluate the analytical solution for a wave travelling in a homogeneous, infinite media. For a given source $S(t)$, the wave-field can be calculated at a distance $r$, for a ...
317 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 ...
16k views

### Can large earthquakes happen twice/thrice at the same place within a short timeframe

I want to know if large earthquakes can happen twice in the same region? The reason is that the recent earthquake in Nepal was followed by many after shocks of considerable magnitude. I wanted to ...
409 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 ...
413 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 ...
98 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 ...
72 views

### How sensitive are typical seismometers?

NASA recently landed a seismometer on Mars, with what sounds an impressive detection ability, with press reports gushing it is "able to detect vibrations smaller than a hydrogen atom." A more ...
151 views

### Lights associated with earthquakes?

According to the New Madrid, Missouri web site, during the 1811-1812 earthquakes there were reports of lights coming from the ground due to quartz crystals being squeezed. They call this phenomena “...
692 views

### seismic wave detection standing at the epicenter

If a person is to stand at the epicenter of an earthquake. Is it true that he would not detect P-waves nor S-waves echoing off the mantle core boundary? Since if P-wave that enter perpendicularly ...
2k views

### How do seismic charges help to investigate the subsurface?

In the film Kong: Skull Island, scientists investigate an island's structure by dropping explosive charges from helicopters: Source: YouTube trailer In reality, geophysicists do something similar ...
580 views

### How does moveout correction work in seismic reflection profiling?

When you take a seismic reflection profile you take multiple shots and then stack them together around a common midpoint. Due to the extra distance travelled by the wide angle shots there is a moveout ...
230 views

### Cross-line fold of a towed-streamer survey

On page 29 of the book 3D Seismic Survey Design by Gijs O. Vermeer, Vermeer says that the equation for a maximum fold in a 3D survey is the following: $M = M_i \times M_c$ where $M_i$ is the inline ...
404 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.
2k views

### Why can Thomsen's parameter $\epsilon$ be negative in VTI media?

I just got several well log curves, some of which are Thomsen's parameters. They are a result of interpretation of Sonic Scanner tool measurements (Schlumberger). Negative epsilon values appear quite ...
340 views

### 2018 Swan Islands earthquake tsunami

How come the strike-slip 7.6 M earthquake, occurring January 9th, 2018, produced no tsunami? Has there ever been any produced in this region?
1k 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 ...
95 views

### Using acoustics to measure the composition, density, and hardness of layers

I am an engineering student at Alfred University and some fellow classmates and I are doing a competition, but one of the tasks we need to complete is autonomously measuring the composition, density, ...
396 views

### Global scale seismology experiments / observations disproving flat earth conspiracy?

Recently I've taken an exceptionally unwise interest in the beliefs on conspiracy theorists, in particular flat earthers. Flat earthism has been trending heavily lately and indeed is undergoing some ...
67 views

### Is “seismic energy released” a regionalized variable and can be analyzed using geostatistics?

In geostatistics, we can assess and analyze regionalized variables. Tectonic stresses releases in seismically active regions by occurring earthquakes. We can calculate and estimate the seismic energy ...
82 views

### Is the concept of seismogenic zone still relevant after the 2011 Japan earthquake?

The concept of subduction seismogenic zone, where megathrust seisms occur in a layer between an upper and a lower limit is well documented in the 1990/early 2000 literature : Some example : Pacheco,...
172 views

### How can I calculate the sensitivity of a seismometer?

I would like to know if a specific seismometer can measure 1 micron/sec velocity. I have a few specs from the datasheet but I'm not a seismologist and am trying to figure out how to relate the specs ...
52 views

### Seismic attenuation in mixed gas/water

Imagine I set off an airgun in the ocean and I measure the far-field signature. Then I do the same thing shortly after introducing tiny gas bubbles into the water, and mixing them well. Are there ...
790 views

### Good Open source alternatives to SeisImager & RES2DINV?

Are there any good open source (Linux) alternatives of SeisImager which includes Pickwin and Plotrefa and file formats are .sg2? Same question for ...
613 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 ...
136 views

### Relationship between tides and earthquakes

Ide et al. (2016) suggest that earthquakes (especially those of high magnitudes) are more probable during periods of high tidal stress (during full and new moons). While they show a comprehensive ...