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Questions tagged [seismology]

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

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15 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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0answers
20 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
44 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
54 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
19 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
29 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
16 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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13 views

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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58 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
73 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
48 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
85 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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1answer
86 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
82 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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1answer
192 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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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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42 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
54 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
81 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
162 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
233 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
567 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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2answers
315 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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2answers
372 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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199 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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1answer
143 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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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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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
146 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
66 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
300 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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2answers
474 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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1answer
295 views

How to calculate cumulative moment magnitude?

What is the proper way to calculate cumuluative moment magnitude if I know the moment magnitude of several earthquakes?
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261 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 ...
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Comparing the 4th of August 1998 earthquake to the 16th of April 2016 earthquake in Ecuador

I'm doing an assignment where I'm comparing the two mentioned earthquakes, and trying to figure out which factors played a role in the amount of casualties. In the 1998 earthquake there were only ...
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1answer
211 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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105 views

Earth's inner core has an inner core inside itself. Are there three inner cores?

The Seeker.com article Earth's Inner Core Has Its Own Inner Core states that researchers at University of Illinois and Nanjing University in China have made a bizarre discovery. They've found that ...
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1answer
611 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 ...
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2answers
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 ...
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1answer
1k 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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1answer
963 views

Can large earthquakes happen few times at same place(in days)

I want to know if large earthquakes can happen twice in the same place? I live in Istanbul/Turkey. In Canakkale/Turkey too many earthquakes happen for days! I know it is normal for this region but 4.8 ...
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1answer
490 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
489 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 ...
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1answer
66 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 ...
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1answer
173 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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2answers
146 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. ...
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0answers
111 views

How to find instrumental response for a seismic station

I received seismic data for which I would like to remove the instrumental response. The only information I have is that they were recorded on a Trillium broadband seismometer with a cutoff period of ...
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1answer
116 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 ...