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Date: December 05, 2024 at 18:42:00
From: pamela, [DNS_Address]
Subject: Magnitude 7.0 earthquake strikes offshore Cape Mendocino, California |
URL: https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F5fb106c1-d00a-441e-b487-35b51a0ed577_1872x1646.png |
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Magnitude 7.0 earthquake strikes offshore Cape
John Vidale shared this from his FB site
Mendocino, California
Reports of shaking >1,000 km away.
Kyle Bradley and Judith A Hubbard
Dec 05, 2024
Earthquake Insights is an ad-free newsletter written by
two earthquake scientists. Our posts are written for a
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A magnitude 7 earthquake struck ~55 km offshore
northern California at 10:44 AM local time on December
5, 2024. This is the ninth earthquake of 2024 to reach
magnitude 7, across the globe — a little low compared
to the annual average of about 14 events per year since
1980 (although this average does include aftershocks of
really big events).
The earthquake caused widespread shaking, reaching
intensity ~VII (very strong) on the coast closest to
the epicenter. Here’s a map showing the estimated
shaking intensity, which is routinely produced by the
USGS National Earthquake Information Center for most
moderate to large earthquakes around the globe:
So far, more than 15,000 people have reported their
experience to the USGS. You can add your own felt
report here. Fortunately, the maximum shaking intensity
was (relatively) limited, because the earthquake
occurred pretty far offshore. The rugged coastline of
Cape Mendocino is relatively sparsely populated. Minor
property damage has been reported, but no injuries.
The quake triggered a ShakeAlert early warning, which
was distributed to people who were expected to
experience at least intensity III or IV (depending on
your settings). For small earthquakes, relatively few
people can benefit from ShakeAlert, because in the time
it takes to detect and characterize the earthquake,
most of the shaking has already occurred. However, for
this larger event, some people were notified tens of
seconds in advance — for instance, people in Fort
Bragg, 146 km to the southeast, should have received 26
seconds of advance notice. To download ShakeAlert onto
your phone, follow the instructions here. To learn what
to do if you receive an alert, click here. Note that
the protocol varies depending on where you are and what
you are doing (e.g. at home vs. driving), so it is a
good idea to review the instructions while thinking
about your daily routine! Chances are you won’t want to
try to look this stuff up on the spot.
A tsunami warning was also temporarily issued after the
earthquake, but was later cancelled. Because the
earthquake was strike-slip, causing lateral rather than
vertical motion of the seafloor, it was not expected to
trigger a tsunami. However, it is always better to be
safe than sorry: even strike-slip earthquakes can cause
underwater landslides, which can create tsunamis.
Because underwater landslides are difficult to detect
(much more difficult than earthquakes), the only way to
be sure this did not happen is to wait and see. When in
doubt, check tsunami.gov for the latest information.
Interestingly, about three minutes after the M7.0
mainshock, a second large earthquake was reported ~250
km to the southeast. The initial reported magnitude of
this second earthquake was M5.8; however, it was soon
downgraded to M4.1. More recently, it was upgraded
slightly to M4.3. We suspect that this event was
triggered by the waves of the first earthquake, but was
mischaracterized because of interference with the
shaking from the more distant, larger earthquake.
Determining the true magnitude seems to be a bit of a
challenge. It is truly fortunate that we have real live
seismologists around to work through the data rather
than relying only on automated systems!
The images below shows two seismographs, with vertical
lines marking the arrival of the P and S waves of the
triggered M4.3 event, which arrived while the stations
were still experiencing the effects of the larger M7.0.
The upper seismograph is from station GCVB, about 18 km
away from the triggered earthquake. The lower one is
from stations SKGS, about 27 km away. Only stations
within ~20 km of the triggered event were able to
record it effectively.
Figure 3: Seismographs from two stations near the M4.3
triggered earthquake, illustrating how the signal was
only clear near the epicenter. Source:
https://ds.iris.edu/wilber3/find_stations/11909389
Tectonic setting
Why is Cape Mendocino such a seismically active area?
Let’s take a look at some data, and also examine some
previous large earthquakes. We have actually written
about earthquakes around Cape Mendocino twice before —
once after a M4.5 earthquake on March 21, 2023, and
again after a M4.7 earthquake on September 30, 2023. So
you can see that earthquakes are not unexpected here,
although of course the recent M7.0 is much larger than
either of those events.
There are basically four potential sources of large
earthquakes in the Cape Mendocino region, each of which
represents a different part of the plate tectonic
system. We like the look of this simple map, taken from
a report on the 1994 Mendocino Fault earthquake
(discussed later):
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[23384] [23385] [23386] [23387] [23389] |
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Date: December 06, 2024 at 07:09:27
From: EQF, [DNS_Address]
Subject: CA Area Quake And High Intensity EM Signals - Dec. 6, 2024 |
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Posted by EQF on December 6, 2024
Hi Pamela and all,
This might be a duplicate of a note that I tried to post earlier today. It didn't look like it registered with the board. So I am trying again.
I am adding the address of that free earthquake service (Earthquake Insights) mentioned in your original note.
https://earthquakeinsights.substack.com/
Two very high intensity electromagnetic signals (EM Signals) were detected on November 29, 2024. I was actually just about to post an earthquake warning to this forum when I saw your post.
Since those warning signals were detected I have been watching this forum to see if any Earthquake Sensitive people or other people had been detecting any especially strong earthquake warning signals. But I didn't see anything along those lines that looked unusual.
I processed the EM Signal data through my earthquake forecasting computer programs. But the nature of the EM Signals indicated to me that it would likely be difficult to use them to tell where the expected earthquake could occur, only that one was getting ready to occur. My best guess was that it would be somewhere in the southwestern Pacific ocean area.
I would not have guessed that one might be about to occur off the coast of California.
Now that the CA area earthquake has occurred I am going to process the earthquake data and see my EM Signals were a good match for that CA quake. I will also be checking several other earthquake forecasting Web sites to see if anyone else was expecting a powerful quake.
An update will be posted here with the results. That should be some time later today.
Finally,
I hope that the CA area quake matches my EM Signals. I was expecting that this could be a fairly destructive earthquake if it occurred near a large city. It sounds like there was no major damage.
So, we have recently had two strong earthquakes occur that could have been highly destructive. There was the one in the Cuba area a while back. Now there was one in the CA area. These earthquakes should be serving as warnings that the scientific community is long overdue with getting some effective earthquake forecasting computer programs running. I have one myself. It just needs to be translated from an ancient version of Perl to some modern language such as Python so that scientists around the world can make use of it and add refinements.
These are personal opinions.
Regards to all,
EQF
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Date: December 06, 2024 at 09:30:50
From: EQF, [DNS_Address]
Subject: WOW - That Was It! - Dec. 6, 2024 |
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Posted by EQF on December 6, 2024
As stated in the above post,
On November 29, 2024 (depending on the time zone) I detected 2 very high intensity EM Signals.
The data for those signals and the recent high magnitude California area earthquake and some of its aftershocks were just processed by my Earthquake Forecasting computer programs.
WOW !
The matches are virtually perfect !!!
Without going into detail, if other and more complex data processing steps were taken with the my computer programs, the two EM Signals, and data from other forecasting Web sites were used, that powerful California area earthquake could probably have been accurately predicted.
What I have repeatedly said over the years is that earthquakes don't occur in the area where I live and work, and I don't have time to watch for other people's earthquakes. The more complex data processing steps would have to have been taken by U.S. West Coast earthquake researchers.
I checked two other earthquake forecasting Web sites to see if either of them spotted the earthquake's approach.
I am not certain regarding what Dr. Lowell Whiteside is stating on his Web site. I can't tell if he was able to see the earthquake coming.
Ground tilt data from a Europe - Asia area Web site indicate to me that one of their charts appears to match my own data and might have been pointing to the earthquake's approach.
Their ground tilt data and my EM Signal data are often in very good agreement in spite of the facts that the two forecasting methods are dramatically different from one another and are even collecting data from different continents.
I am planning to create a new Web page at my newest earthquake forecasting Web site. That Web site is complicated to use. The Web page editor I am using is not very sophisticated and creating new Web pages and uploading files can be a tedious process. The new site is not yet operational to the desired extent. That is why I haven't yet released the address of the new site.
If I do manage to get this work done today I will store these CA quake data on the new Web page and post the address of the new Web page here.
These are personal opinions.
Regards to all,
EQF
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Date: December 06, 2024 at 11:32:01
From: jordan, [DNS_Address]
Subject: Re: WOW - That Was It! - Dec. 6, 2024 |
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thanks for posting but it does not count if not posted
after quake
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Date: December 06, 2024 at 13:15:39
From: EQF, [DNS_Address]
Subject: Re: WOW - That Was It! - Dec. 6, 2024 |
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Posted by EQF on December 6, 2024
Actually, it does count, in my opinion.
This is part of a highly sophisticated earthquake forecasting research effort that has been underway for more than a decade. See another post that will point to an earthquake forecasting Web page that I created in just the past few hours.
Experienced scientists know (I have 2 degrees) that with complex subjects such as earthquake forecasting, it is critically important to let everyone know if any progress is being made regardless of the time that some earthquake precursor data have been collected.
It required so much time for me to get this new earthquake forecasting Web site operational that my EM Signal processing and notification got quite a bit behind. I am only now catching up with things. That is why I did not post a note about those high intensity EM signals when they were first detected.
Finally,
The highly advanced earthquake forecasting research that I am doing might actually represent the best chance that we have of developing effective earthquake forecasting programs. Other researchers have been attempting this for years. Right now, with my own efforts, I probably only now need to get computer programmers using a language such as Python to create a usable version of my main earthquake forecasting computer program.
I am not a professional computer programmer. My attitude is that if a program works, then that is good enough for a basic effort. My formally copyrighted computer programs have been available for free use for years. Professional computer programmers who have seen them have gotten frightened out of their wits. They are so complex and use so many
IF Then GoTo
commands that they are in fact pretty scary. It can take me hours or even days to just determine where in the main program I need to add some new code when that is necessary.
These are personal opinions.
Regards to all,
EQF
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Date: December 06, 2024 at 14:46:05
From: jordan, [DNS_Address]
Subject: Re: WOW - That Was It! - Dec. 6, 2024 |
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sorry I did not know It required so much time for me to
get this new earthquake forecasting Web site operational
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