Questions tagged [seismology]
For questions about the study of earthquakes and various seismic sources.
147
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29 views
Zoeppritz equations derivation
I have been long looking for the derivations and step by step explanation of Zoeppritz matrix but either internet is full of final versions or I can’t find it...I would be very thankful if anyone can ...
2
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1answer
48 views
Can a rock have a Vp of less than 1000 m/s and need blasting to excavate?
I have run a 60 m refraction seismic line on a mountain summit. The environment was noisy (wind would be the principal agent) and quite difficult to pick first arrivals. It resulted in 800 m/s.
A ...
0
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1answer
27 views
Is it reasonable to approximate the swinging building (base of the building) during an earthquake to a simple harmonic motion?
I am thinking of making a model of swinging building during earthquake and study the methods to minimize the swinging.
So does it even makes sense to approximate the swinging buildings (the base of ...
3
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50 views
Wave train 200 m/s meaning
I ran a 60 m line intended for surficial seismic refraction. Energization with hammer. 12 (10 hz vertical 5 m spaced) geophones and 5 shots (15 m spaced). Record length 0.5 s. Thanks to a borehole ...
3
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1answer
49 views
Where can I download historical sesimic data in CSV/Excel format for processing in R?
I'm not familiar with these kinds of data sets but I'm looking for some data for a project I'm working on. Essentially I would like multiple time series of seismic data from different stations over ...
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1answer
44 views
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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1answer
38 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
35 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 ...
4
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1answer
133 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 ...
2
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2answers
154 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 ...
0
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1answer
47 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
42 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
18 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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14 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 ...
3
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0answers
62 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 ...
6
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1answer
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 ...
9
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1answer
105 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 ...
2
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0answers
55 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
190 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 ...
5
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1answer
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, ...
2
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1answer
94 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 ...
4
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1answer
199 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 ...
3
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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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46 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
58 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
87 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 ...
3
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1answer
218 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 ...
3
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1answer
267 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?
4
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1answer
741 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 ...
5
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2answers
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?
4
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2answers
509 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
57 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 ...
2
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0answers
212 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 ...
6
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1answer
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 “...
4
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1answer
3k 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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355 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?
5
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1answer
173 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 ...
2
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1answer
71 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 ...
3
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1answer
344 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 ...
3
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2answers
593 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. ...
2
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1answer
351 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?
7
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1answer
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 ...
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0answers
68 views
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 ...
4
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1answer
226 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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0answers
116 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 ...
6
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1answer
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 ...
6
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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 ...
13
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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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1answer
1k 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
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 ...
