Depths of earthquakes - particularly deep earthquakes

  • Thread starter Astronuc
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In summary: The popular press has an obligation to get these things right, not to mention the editors who are supposed to be the "last line of defense."In summary, a recent article from the LA Times reported on the discovery that earthquakes can occur much deeper below the Earth's surface in California than previously believed. This was attributed to scientists finding evidence of earthquakes occurring more than 15 miles underground, which challenges the long-held belief that earthquakes only occur in the planet's brittle, rocky crust. However, this is not a new discovery as deep earthquakes have been observed for decades. The misinterpretation and sensationalization of this news has caused frustration for those knowledgeable in the field. Additionally, the recent discovery of the Salton Trough Fault was also mentioned,
  • #1
Astronuc
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I just read a headlines about "Earthquakes in California are discovered more than 15 miles deep."
https://www.yahoo.com/news/m/e994149f-34a9-3ab4-b16f-fd382e41b607/ss_earthquakes-in-california-are.html
Apparently that's a surprise for California. The article is attributed to the LA Times.

Then there is the first sentences, "Scientists in California have found that earthquakes can occur much deeper below the Earth’s surface than originally believed, a discovery that alters their understanding of seismic behavior and potential risks. Seismologists have long believed that earthquakes occur less than 12 to 15 miles underground in the planet’s brittle, rocky crust." However, we've been watching deep earthquakes, deeper than 15 miles for decades. One can find records on deep earthquakes on USGS.

For example,
M5.0 - 14km SSE of Las Navas, Philippines
2016-10-06 19:09:50 UTC 12.211°N 125.076°E
61.5 km depth
 
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  • #2
Astronuc said:
Apparently that's a surprise for California. The article is attributed to the LA Times.
Have you read about the second fault next to the San Andreas fault they allegedly have found some days ago?
 
  • #3
Localized seismic deformation in the upper mantle revealed by dense seismic arrays---http://science.sciencemag.org/content/354/6308/88. I was a bit stunned by all the media hype. Interestingly, the paper presents it more matter-of-factly. The real surprise in their work was that the Newport-Inglewood Fault possibly extended down to the mantle. In my last years of oil exploration in California, we had seismic data that showed major boundary faults in California and Nevada extended to the mantle. By 2001, that knowledge was the basis for pretty redefining the tectonic model of the western US. I don't recall quake intensities and depths along those faults, but it should be no great surprise that they would be deep.
 
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  • #4
The "discovery" of the Salton Trough Fault is a bit odd. I can understand how the underwater portion might have been missed all these years, but it apparently tracks close to the San Andreas Fault onshore. Not so close that it couldn't be distinguished from the SAF.
 
  • #5
fresh_42 said:
Have you read about the second fault next to the San Andreas fault they allegedly have found some days ago?
Well, it looks like they recently announced the discovery in the current issue of the Bulletin of the Seismological Society of America.

Geophysical Evidence for a San Andreas Subparallel Transtensional Fault along the Northeastern Shore of the Salton Sea
http://www.bssaonline.org/content/106/5/1963.abstract
"This study posits that the extensional deformation is due to a previously unmapped fault, here named the Salton trough fault (STF)."

New Southern California earthquake fault found near San Andreas
http://www.desertsun.com/story/weat...trough-fault-salton-sea-earthquakes/91609892/

Valerie Sahakian, a researcher with the U.S. Geological Survey and lead author of the study, said the newly named Salton Trough Fault has no connection to the recent quake swarm and the timing of the announcement is coincidental.

http://time.com/4521244/new-fault-line-california-salton-trough/

http://earthquake.usgs.gov/hazards/qfaults/map/#qfaults (is it the red dotted line on the eastern side of the Salton Sea?)
 
  • #6
Astronuc said:
I just read a headlines about "Earthquakes in California are discovered more than 15 miles deep."
https://www.yahoo.com/news/m/e994149f-34a9-3ab4-b16f-fd382e41b607/ss_earthquakes-in-california-are.html
Apparently that's a surprise for California. The article is attributed to the LA Times.

Then there is the first sentences, "Scientists in California have found that earthquakes can occur much deeper below the Earth’s surface than originally believed, a discovery that alters their understanding of seismic behavior and potential risks. Seismologists have long believed that earthquakes occur less than 12 to 15 miles underground in the planet’s brittle, rocky crust." However, we've been watching deep earthquakes, deeper than 15 miles for decades. One can find records on deep earthquakes on USGS.

For example,
M5.0 - 14km SSE of Las Navas, Philippines
2016-10-06 19:09:50 UTC 12.211°N 125.076°E
61.5 km depth

seems typical of really bad reporting and mis-interpretation of what the seismologists probably said
this sort of mis-information really annoys me

we all know ( those of us into this stuff, at least) that quakes go much deeper than 10 - 15km
eg. the Philippines one mentioned and on terms of deep earthquakes, that one is really shallow
when the large subduction zones are looked at with quake depths to well over 600 kmDave
 
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  • #7
davenn said:
seems typical of really bad reporting and mis-interpretation of what the seismologists probably said
this sort of mis-information really annoys me

we all know ( those of us into this stuff, at least) that quakes go much deeper than 10 - 15km
Indeed. The detection of ever deeper quakes, defining a descending plane, was one of the key pieces of evidence leading to the recognition and acceptance of plate tectonics. It astounds, frustrates and angers me when popular accounts make such egregious errors.
 
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1. What is the depth of an earthquake?

The depth of an earthquake is the distance between the earthquake's focus (the point where the earthquake originates) and the Earth's surface. It is typically measured in kilometers.

2. How deep can earthquakes occur?

Earthquakes can occur at various depths, but the majority of earthquakes happen at depths of less than 70 kilometers. However, some earthquakes, known as deep earthquakes, can occur at depths of over 300 kilometers.

3. What causes deep earthquakes?

Deep earthquakes are caused by the movement of tectonic plates, which are large pieces of the Earth's crust that move and interact with each other. When these plates move, they can create stress and pressure that can cause earthquakes at various depths.

4. Are deep earthquakes more dangerous than shallow earthquakes?

Generally, deep earthquakes are not as dangerous as shallow earthquakes because they occur so far below the Earth's surface. However, they can still cause damage and can be felt by people living nearby.

5. How do scientists measure the depth of an earthquake?

Scientists use a variety of methods to measure the depth of an earthquake, including seismometers, which record the seismic waves produced by the earthquake. By analyzing these waves, scientists can determine the depth and location of the earthquake's focus.

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