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Questions tagged [seismology]

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

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1answer
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wave speed is smaller than both horizontal wave speed and vertical wave speed?

I am new to GIS and just get the idea of slowness. I can understand why people need the slowness in GIS rather than just the reciprocal of velocity. However, I feel the definition of slowness is weird ...
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2answers
80 views

Travel Times for Seismic Wave Types - Why reflected t-x plot curves

I do not understand how the reflected wave in a seismic survey has a steepening slope (slows down) Please bear with me as I lay out my thoughts because I feel like I can grasp all of this except this ...
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1answer
27 views

Near-Surface Investigations: FWI vs. MASW

MASW is a common processing method for civil/geotechnical and even for oil/gas exploration (usually weathering static corrections) applications. In my experience, it seems to work well for most ...
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1answer
59 views

How does multiple layer seismic reflection work? How do we distinguish arrivals from different layers and their velocities?

Whenever we are investigating multiple layer interfaces in a seismic reflection survey the root-mean-squared velocity is often employed to deduce travel time to a certain n-th layer and also to deduce ...
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1answer
503 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 ...
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1answer
25 views

reverse time migration for wave equation PDE using SBP-SAT

I'm stuck implementing a reverse time migration technique, the PDE(partial differential equation) being implemented is an acoustic wave equation, The numerical method being used is a FD(finite ...
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1answer
145 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 “...
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0answers
26 views

What are “young thrust faults” and why are they significant on the Moon?

The abstract of the new Nature Geoscience paper Shallow seismic activity and young thrust faults on the Moon reads: The discovery of young thrust faults on the Moon is evidence of recent tectonic ...
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1answer
153 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 ...
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1answer
311 views

What are the physical upper bounds on the magnitude of an earthquake?

Given what we know about the physical mechanisms underlying earthquakes, what do the theoretical upper bounds on the magnitude of an earthquake look like? What physical phenomena impose those upper ...
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2answers
767 views

How does one measure what causes earthquakes?

I know that they occur when energy that was previously stored is released in seismic waves. But how is the energy stored in the earth in the first place, and what can trigger the release of such ...
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3answers
381 views

Is fracking likely to produce earthquakes?

Post Christchurch-2011 earthquake, there was much concern that fracking in the surrounding areas might lead to further quakes, as was rumoured to have happened elsewhere in the world. Is there ...
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3answers
9k views

Is it true that earthquakes are not felt in a cave?

I took a tour of a cave in northern California last weekend. The tour guide asked us, "If an earthquake occurred, what would we feel in here?" My answer was, "fear," but she said we would feel ...
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6answers
93k views

Are Richter-magnitude 10 earthquakes possible?

The largest earthquake since 1900 according to the United States Geological Survey (USGS) was Richter-9.5 magnitude quake in Chile in 1960. Are magnitude 10 earthquakes possible? If so, what is the ...
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1answer
30 views

Love-Wave Propagation

Love-waves cannot exist in a half-space. Layering must be present and there also must be accompanied impedance contrasts associated with the layering. Because layering naturally induces seismic ...
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1answer
17 views

Does the shear modulus of silicate minerals vary significantly with changes in P and T?

I know that the bulk modulus, K, varies with pressure and temperature for silicate minerals and liquids, but what about the shear modulus? If so, is the change drastic for changes from standard ...
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0answers
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Determining the spatial orientation of a fault given ground acceleration magnitude in different directions

Accelerographs measure ground acceleration in three different components of motion: east-west, north-south, and vertically (up-down). I know that fault orientation is important here, so let's say we ...
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0answers
59 views

Rayleigh waves generation

Good day, I do not fully understand the physical mechanism of formation of Rayleigh waves at the free surface. While their derivation is quite clear and obey free-boundary conditions, it is not clear ...
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1answer
55 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 ...
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1answer
174 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 ...
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1answer
217 views

What (if anything) can be learned from accurately recording tilt motion during seismic events?

The Rotational Motions in Seismology (ROMY) instrument is a giant laser gyroscope used to generate extremely precise 3D rotation measurements of planet Earth. However at the end of the video below ...
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1answer
76 views

Could an earthquake create a design in a sand pendulum?

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 ...
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0answers
49 views

Difference between landslide waves and earth quake waves

I am new to this field, recently started working on landslide monitoring mainly in signal processing part. I have the following questions? 1.Will each land slide and every vibration have p wave, s ...
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1answer
102 views

Quality control in Seismic Acquisition - How much data is required?

When it comes to land or marine acquisition (oil exploration, for instance), I can see from literature that quality control (QC) is performed during the survey to ensure that the seismic traces ...
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3answers
4k views

Do other terrestrial planets have “earthquakes”?

I know some planets have storms akin to what we have on Earth although obviously varying in nature. I was wondering if other planets have earthquakes? Since this comes down to plate tectonics (right?...
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1answer
174 views

Open source well information viewer

I am in the middle of a hobbyist experiment and would like suggestions on an open source HTML viewer for mud loggging, FMIs, lithology and seismic. I have used INT before but for this project I would ...
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1answer
94 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, ...
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1answer
193 views

Why do major earthquakes keep happening in Lombok recently?

So I've been following the situation in Lombok, Indonesia from both online news and friends on the ground. One thing that I can't seem to figure out is why there are so many earthquakes over an ...
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1answer
387 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 ...
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1answer
85 views

Could glacial melt alter plate tectonic movement?

Let's say some event caused runaway glacial melt, and removed half of the ice currently locked away in specific areas of the planet. Would the significant weight changes on various plates and fault ...
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0answers
33 views

statistical methods for analysis of stability tailored for multiple short time series

I am a graduate student of Ecology working on a species diversity problem and am not much educated in time series methods. i have searched 3 general time-series books and could not find a clue on how ...
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0answers
43 views

Seismology - PPV / VDV from geophone waveform data

I'm using an inexpensive seismometer to try and measure the effects of local HGV traffic on buildings. The device is connected to a Raspberry PI that has a Cirrus Logic Audio Card. The signal is fed ...
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1answer
55 views

What does 'reghosted' mean in a seismic cube label?

I came across to a seismic volume labeled as reghosted. In my understanding, a seismic survey is deghosted as part of a processing step. Then I wonder why one would like to reghosted the data? Is ...
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3answers
83 views

Need seismic data and digital well log data from the same area?

I am currently working on a project that involves the input of seismic attributes (instantaneous amplitude, instantaneous frequency etc.) to a machine learning/deep learning model (eg. A Neural ...
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1answer
243 views

Which type of seismic sensors usually used in Earthquake Early Warning?

As I'm a newbie in seismology and related area, I would like to know which type of seismic sensors usually used in earthquake early warning systems?
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1answer
2k views

Using accelerometer as a seismograph

I'm using ADXL345 accelerometer with Raspberry Pi to build a seismograph. I've successfully hooked it up and can plot the accelerometer data in three axis. Is there any way to express these data in ...
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2answers
321 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?
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1answer
2k views

SEGD and SEGY recorded data

What is the difference between a segd recorded data and a segy recorded data and can we convert from segd to segy and vice versa?
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4answers
12k views

How can we determine the size and composition of Earth's inner core?

From Wikipedia: Earth's inner core is Earth's innermost part and is a primarily solid ball with a radius of about 1,220 km (760 mi). (This is about 70% of the Moon's radius.) It is believed to consist ...
4
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1answer
594 views

What is the relationship between raw seismic data, CMP Stacking, NMO & Machine Learning

I recently joined a geophysics project to assist with some of their machine learning modeling but am trying to gather the domain knowledge required to participate. Something I don't quite understand ...
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0answers
212 views

How to compute the earthquake occurrence probability under ETAS model

I have fitted an ETAS model (unmarked) with an independent exponential magnitude distribution to a set of earthquake data. However, I do not know how to calculate the probability of the earthquake ...
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2answers
403 views

Acoustic impedance in geophysical context

What is the intuition behind acoustic impedance? Yes, I know that it is the opposition to a seismic wave travelling in the medium. But why it is defined as density × velocity? The velocity of a ...
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0answers
53 views

Problem in identification of seismic event?

I have taken the following synthetic seismogram, generated using Marmousi model, from the Madagascar website. I could not understand the origin of linear events (present in shot3 after 2 sec) and ...
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0answers
204 views

How to calculate seismic moment from seismograms?

I was told that Seismic moment is determined by the observed spectral levels of the receiving waves. But I don't quite understand what it means. How is this done in practice? Do you need ...
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2answers
519 views

Seismometer records ground displacement or acceleration

I believe Seismometers record ground displacement. However, I have also read in certain articles that this can be ground displacement or acceleration depending on the frequency of the seismometer. ...
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0answers
352 views

Effects of Mexican Earthquake in San Andreas Fault Line

Could the recent 8.1 Magnitude Earthquake at the Cocos and Nazca plates off the Mexican coast have a knock on effect to the Pacific and Juan de Fuca Plates further north at the San Andreas Fault Line?
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1answer
68 views

Is the centre of Italy still at risk of earthquakes?

I am working on a project which involves taking over a business based in Italy. It is a small village situated near Rieti (Sabina Hills) called Casperia and I am wondering if it is on a fault line? Is ...
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1answer
308 views

What causes ringing effect when using corner filter?

I used the corner filter (band pass) with this frequency values (8,10,45,50). I get ringing effect on the data. my questions are: what is the name of this effect and the cause? should be removed and ...
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5answers
4k views

Why aren't seismic stations installed very deep underground so as to pre-warn from earthquakes?

The velocity of p-waves emanating from earthquakes is in the range of 5-8 km/s (link)--let's assume it is 5 km/s. The earthquake depth is up to hundreds of kms deep underground (link)--let's assume it ...
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1answer
223 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 ...