Questions tagged [seismology]
For questions about the study of earthquakes and various seismic sources.
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Will California become a subduction zone in the distant future
California is one of the few places in the world that lie on a transform fault. My question is why considering the fact that North American Plate is moving westward shouldn't California be a ...
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21 views
Is it possible for Mexico to have a magnitude 9 earthquake?
Everyone has heard of the Cascadia Subduction Zone and the potential threat it poses. However, I have heard nothing about The Cocos Subduction Zone, even though it caused a devastating earthquake over ...
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1answer
29 views
What would be the phase shift and polarity of a seismic wave upon reflection
What would be the phase shift and polarity of a seismic wave a) when it hit the free surface
b)when the free surface reflection goes down and hit a reflector and returned to the receiver placed on the ...
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72 views
What condition(s) need to be met to be able to determine the hypocenter of a microseism?
Today, this XKCD popped up in a chatroom:
comic CC BY-NC 2.5 linked to the source
User Rob mentioned that (as usual with XKCD) this is based on the findings in a research paper.
In Source location of ...
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29 views
Beam forming FK analysis of a seismic wave
So after reading alot of literature on source localization, I found out that FK analysis is one of the most widely used methods to determine source location without explicitly calculating the ...
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21 views
How all of the files listed as stream (st) could be used or listed as traces (tr) in obspy (python)?
PPSD (seismic background noise)
I list all of my files, basically as components (H1, H2, and V), as streas as follows:
import os
from obspy import read
from obspy.signal import PPSD
import ...
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1answer
78 views
How do we know the speed of S-waves (shear waves) in the Earth's inner core? Has this been measured?
Wikipedia's Seismic wave includes the plot below of the speed of S and P waves as a function of depth in the Earth. In the region of the outer core the speed of S-waves or shear waves is shown to be ...
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4answers
322 views
Do we know anything about the nature of Earth's core that hasn't come from magnetic or seismic measurements?
There is much known about Earth's core from painstaking analysis of seismic data, and from detailed magnetic field maps and trends over time.
Are there any other measurements that have contributed to ...
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1answer
89 views
Performing time-frequency analysis (FTAN)
I am trying to do ambient noise tomography and I am quite confused on how to perform time-frequency analysis (FTAN) as shown in figure 13b and 13d of this paper by Bensen et al.. I am using Python and ...
3
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1answer
52 views
What are today's methods in calculating the Local Magnitude of earthquakes?
I'm no expert and barely have any idea about this. But I want to know if the methods in calculating the Local Magnitude can only be done manually? I mean manually by first reading a seismograph, ...
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1answer
55 views
Where can I find broadband seismic reflection data?
or what type of companies should I contact to ask for the data?
This data would be produced from Seismic Vibroseis survey trucks which are mostly used to locate oil and gas.
I doubt most oil and gas ...
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88 views
Small earthquake happening every night at the exact same time
I experience this weird feeling for the last three months. Every night, at exactly 3AM I can feel small earthquake and I could not find anything on the internet related to it. Does anyone have any ...
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2answers
283 views
How to read and plot seismic waveform data in Ascii format using Obspy?
I wish to plot seismic waveform data using Obspy, bu they are in Ascii format. Is it possible to read and plot Ascii file using Obspy?
2
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1answer
56 views
Using an accelerometer as a geophone to conduct a seismic survey
I am doing a capstone project for a sensor systems course and I would like to write a python program to acquire, process and present seismic data like that of seismic surveys. Is it possible using ...
0
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1answer
77 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 ...
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2answers
102 views
Can an igneous 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 ...
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1answer
38 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 ...
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1answer
84 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 ...
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1answer
62 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
73 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
81 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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78 views
What are “young thrust faults” and how does one identify them 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
310 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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2answers
343 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
75 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
48 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
21 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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15 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
74 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
85 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
179 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
57 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
302 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
100 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
107 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
203 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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58 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
63 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
132 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
298 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
272 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
953 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
365 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
741 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
58 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
231 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
172 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
4k 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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356 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?
