# Tag Info

37

Adding a little bit of practical data to the above answer about the Gutenberg-Richter relationship, here is a plot of the per-year cumulative probability of earthquakes in a particular province in Japan, based on observed frequencies over many hundreds of years: Source: http://topo.earth.chiba-u.jp/afr/backnumber/no24/24%E5%8F%B702kumamoto.pdf The ...

34

Are magnitude 10 earthquakes possible? The idea of a “Mega-Quake” – an earthquake of magnitude 10 or larger – while theoretically possible—is very highly unlikely. Earthquake magnitude is based in part on the length of faults -- the longer the fault, the larger the earthquake. The simple truth is that there are no known faults capable of ...

34

Magnitude 10 earthquakes are indeed possible, but very very unlikely. You see the frequency of an Earthquake is given by the Gutenberg-Richter law: $$N = 10^{a-bM}$$ where $N$ is the number of earthquakes $\ge M (magnitude)$ and $a,b$ are constants. As you can see, the greater $M$ is, the less $N$ is. $a,b$ are generally solved for statistically, through ...

28

The simple answer is that you can't drill to 50 km depth. The deepest holes ever drilled were to a little more than 12 km, one is named the Kola Superdeep Borehole in Russia, which was a scientific drilling project. The very few others were oil exploration boreholes. Drilling that deep is extremely expensive and hard. If you go and ask anyone who ever ...

26

Yep, mining can trigger earthquakes. According to a Scientific American article: We've been monitoring [The Geysers] since 1975. All the earthquakes we see there are [human] induced. When they move production into a new area, earthquakes start there, and when they stop production, the earthquakes stop. This is talking about geothermal power. They create ...

26

10 seconds is a worthwhile warning time. The Japanese use it to switch off compressors on gas lines (or open release valves on them), emergency break bullet trains, and in particular shut down nuclear power plants, all in anticipation of a power loss moments later. In the case of Japan, however, the warning time doesn't come from having deep sensors, but ...

26

It is called "antipodal focusing". See for example Antipodal focusing of seismic waves observed with the USArray. We present an analysis of the M-w = 5.3 earthquake that occurred in the Southeast Indian Ridge on 2010 February 11 using USArray data. The epicentre of this event is antipodal to the USArray, providing us with an opportunity to observe in ...

25

Ground motion results due to passage of elastic waves. Now there are different kinds of waves, e.g., P waves, S waves, surface waves, etc. Most of the shaking (and therefore damage) is caused by surface waves. So if you are in a deep cave or mine then the amount of shaking you might experience can be much lower than on the surface. This of course assumes ...

21

Perhaps this is not what you had in mind, but it seems to be generally agreed that the Chicxulub asteroid impact generated earthquakes in excess of magnitude 10.

21

The main proxy that we have of past solar intensity comes from its proven correlation to the number of sunspots, which have been recorded since the invention of the telescope in the early 1600's. And the plot looks like this: We have no evidence of any significant correlation between the solar cycle and earthquakes or volcanic activity. You won't find ...

20

It's not too too likely, but it can happen. A few earthquakes have either been attributed to fracking, or the wastewater produced from fracking. According to the USGS (for more information, visit that page): Many questions have been raised about whether hydraulic fracturing — commonly known as “fracking”— is responsible for the recent increase of ...

20

Earthquake prediction really is a contentious issue, especially after the l'Aqula trials. However, let me try to elaborate how predictions might be possible in the future and what is inhibiting this development. We do have some understanding of earthquakes and rupture mechanisms. However, for prediction in a scale of hours (sufficient for evacuation), we ...

17

You ask what we should change to better predict earthquakes, and I'd think almost everything. As geophysicists we might know the what of earthquake detonation, but are relatively blind at the how. There is a strong group of scientists who feel that single event prediction is NOT a realistic goal, and may perhaps be impossible. Some good guesses as to why ...

17

The Short Answer is Yes. The consensus is that humans can prematurely trigger earthquakes, and this paper in 1986's EPSL annual reviews seems to be in full support. There is also this paper which suggests that mining induced earthquakes are quite common. A third paper published in Science last year also suggests that hydraulic fracking can cause earthquakes. ...

17

To my knowledge, the best study looking at potential explanations for the Red Sea crossing is the one by Nof and Paldor (1992). They present a couple of plausible scenarios for the crossing. The main one is the effect of strong winds blowing along the Gulf of Suez and they find that the sea level drop could be sufficient: It is found that, even for ...

17

There are three main types of waves produced during an earthquake: P, S, and L waves, which stands for Primary, Secondary, and Love. (There was a mnemonic I read many years ago that went P=pressure, S=Shear, and L=Long.) The P and S waves are body waves. That is, they propagate inside the earth. The P wave is basically a sound wave; as the mnemonic goes, a ...

15

Earthquake epicenters are located using triangulation, this is possible once seismograms of the earthquake - coming from at least three locations - have been analyzed properly. Here is a good explanation on a site for seismology students at Michigan Tech which takes its seismogram illustrations from Bolt's textbook on earthquakes (1978). Read this page and ...

15

Googling leads to a very old document: EFFECTS OF AN EARTHQUAKE IN A MINE AT TOMBSTONE, ARIZONA stating that in many cases, mine workers did not notice earthquakes which were felt above ground. A newer book, Earthquake effects on tunnels, check the "Look Inside" option for the introduction) confirms this. According to this source, a possible reason is that ...

14

There are a number of causes (this list is probably not complete): Elastic Rebound of tectonic faults. This is the most common and well known. Here the energy is elastic energy stored as two blocks of rocks move against each other. There is a point where elastic deformation cannot take up the entire movement, and the rock breaks releasing the elastic energy....

14

These two images probably explain it best: This is a map from the US Geological Survey Earthquake Hazards Program, which shows all recorded large earthquakes in the region from 1900 to March 2012. The black lines are tectonic plate boundaries. The plate in the middle is the Arabian Plate. The current movement of that plate is show in this image from ...

14

Is it possible for Earth to experience Polar Shift? Yes, and it has happened before. In the past 80 million years it happened over 150 times. The last time this happened was around 800 thousand years ago. A quick note about what a polar shift is, more properly termed a geomagnetic reversal. Earth's magnetic is such that a compass points to a certain ...

14

You're asking Why do human populations concentrate near fault lines, volcanoes, etc.? But the real question is Do human populations concentrate near fault lines, volcanoes, etc.? And the answer is not necessarily positive. Let's look at where earthquakes are: and active volcanism: Both maps are from Volcano Discovery. Here's a population density ...

14

Several things can indicate that a seismic event is an explosion and not an earthquake. Firstly, the depth of the source. The shallowest earthquakes tend to have a hypocentre that is at least a couple of km below the ground surface and some earthquakes in certain parts of the world can go down to about 700 km. Artificial explosions on the other hand, will ...

13

Besides the theoretical limitations that @Neo talks about, there is also a great data gap in our knowledge. To predict an earthquake, we would need to know: The 3D geometry of all major, and possibly minor, fault zones The distribution of stress in the lithosphere, at least close to the fault zones but possibly more The physical characteristics of the rocks ...

13

The 2011 AGU poster has been cited once, by Burtin et al. (2013)1, who say in their abstract ... event activity was positively correlated with the precipitation intensity... -- but more importantly, in the body of the paper, this: Furthermore, it has been argued that rainfall may affect the occurrence of earthquakes, either by downward fluid diffusion ...

13

Is it possible that the recent droughts are signs of epic crust failure? No. Even though your 5 points do not make much sense, I'll try to answer it anyway. There are no continental plates. There are lithospheric plates, consisting of both continental crust and oceanic crust. While it is true that arches in construction (buildings and bridges) are held "up"...

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Crustal plates are not homogeneous, uniformly continuous rock masses with uniform stresses. They are a mixture of rock types with variable stresses and stress concentrations. They are also discontinuous. There are fault zones within plates. Some faults are active & others inactive. When movement occurs along an active fault, usually due to in-plate ...

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There isn't a concentration of tectonic plates - rather the opposite! The "Ring of Fire" is a pattern really. It is marked by subduction zones. So the question becomes, "Why is the Pacific Ocean surrounded by subduction zones?". Think back to Pangaea. This was a supercontinent that formed in the late Palaeozoic. Virtually all of the Earth's land masses ...

12

Well the dinosaur-killing asteroid that struck the Yucatan peninsula in the gulf of Mexico (65 million years ago!) generated a seismic shock or earthquake that went around the world and registered magnitude 13 on the Richter scale the reason for this was the object was 6 miles in diameter and its mass was equal to all the construction-materials used for ...

12

By definition, the answer is yes: epicenter, the point on the earth's surface vertically above the focus of an earthquake, or the Hypocenter according to Merriam-Webster or a many other sources.

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