Questions tagged [seismology]

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

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13 views

How can you find the seismic intensity at a given point?

Given the distance, material, and seismic intensity at the epicenter, can you calculate the seismic intensity at a given point?
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3answers
603 views

Are there any techniques for imaging the deep Earth besides seismic waves?

It is well-known that we can learn a lot about the structure of the lower crust, mantle, and core by observing the ways in which they refract different kinds of seismic waves. Do we have any other ...
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1answer
26 views

Source for USGS (probably not) seismic map of La Habra, California (Publication Date April 15, 1998)

I'm trying to find to original source (especially high quality version) of this conservation seismic map. I know that it probably came from USGS (or not) but looks like it out of print? I tried to ...
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1answer
1k 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
157 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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2answers
45k views

How do seismologists locate the epicenter and focus of an earthquake?

I know the focus of an earthquake is where the earthquake originated from, but what I could never figure out is, how to scientists find out where exactly the focus (and epicenter) are located?
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1answer
92 views

Where can I find an anisotropic PREM-like model for Earth's interior?

So, I just discovered PREM (the Preliminary reference Earth model) which models the density distribution of matter inside the Earth to any depth. The PREM is very convenient but since it only depends ...
15
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1answer
247 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
208 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 ...
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20 views

Quality control in Seismic Acquisition - shot offset shift

I have a problem with seismic data where the minimum offset of the shot is not centered at the nearest receiver, this shift can be for 3 traces 2 or one and maybe more in the two sides !! So is there ...
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1answer
235 views

Does the Earth produces measurable gravity waves?

Does the Earth exhibit measurable gravity waves? Note: I'm not asking about gravitational waves. Some recent experiments looking at low-frequency (3$\times 10^{-5}$Hz) accelerometer data are showing ...
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1answer
2k views

Why are there more intense earthquakes in Iran than in Iraq?

Why are there more intense earthquakes in Iran than in Iraq, if they are so close together? I often hear news items of earthquakes in Iran that are higher on the Richter Scale than those that happen ...
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1answer
33 views

Difference between Earthquake Seismographs

How can we tell the difference between a seismograph of a local earthquake and that of a distant earthquake?
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3answers
100 views

Is an Earthquake Large Enough to Cripple the Entire West Coast of North America Possible?

I have an idea for a novel I want to turn into a reality, and I'm starting some research first to make my book at least plausible in very specific conditions. The main aspect of the story would be ...
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19 views

Orientations of the fault plane and the auxiliary plane

How can someone find the possible orientations of the fault plane and the auxiliary plane? This tensor is in the geographical coordinate system North, East and Down, given a moment tensor. M= \begin{...
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47 views

equivalent body force

I am currently reading "Introduction to seismology second edition, and I can't wrap my head around earthquake sources, especially equivalent body force. What is an “equivalent body force” and how ...
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34 views

Horizontal slowness in seismology

I am working on a seismology assignment and it starts with the fundamentals of seismology such as the wave equation, the slowness... such as the question below: write an equation describing the ...
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1answer
5k 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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1answer
410 views

How much silicon is in the Earth's core, and how did it get there?

With some informal conversation with a peer of mine, he had suggested that there is evidence (which he couldn't find,but had remembered reading) that there was Silicon in the Earth's core. I referred ...
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3answers
11k 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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2answers
57 views

Would climate change result in an increase in seismic activities?

Would climate change result in an increase in seismic activities? I can see two potential forces acting: Temperature dilation of the Earth's surface. A change in the distribution of water mass, fewer ...
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1answer
64 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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2answers
371 views

How accurately can explosions be triangulated from the IRIS seismogram data?

There's a bunch of armed conflicts going on right now. What are the lower boundaries on accuracy of triangulating and timing man-made events from the IRIS datasets (accessible, for instance, with the ...
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51 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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4answers
343 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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80 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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1answer
50 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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1answer
61 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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48 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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8answers
3k views

Is earthquake prediction possible?

After the Tohoku and East Coast quakes, I skimmed over several books discussing the validity of earthquake prediction as a discipline, yet found no significant breakthroughs. What should change in our ...
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87 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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2answers
232 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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2answers
564 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?
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1answer
184 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
3k views

Is there a correlation between hot springs and earthquakes?

Is there a correlation between how many hot springs an area has, and how frequent or severe the area's earthquakes are?
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2answers
291 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 ...
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1answer
487 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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98 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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1answer
68 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 ...
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1answer
101 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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1answer
92 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
773 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
39 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
168 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
94 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
115 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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2answers
557 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
82 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
103 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
191 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 “...