Venezuela earthquakes

[Adam Pascale]

In an effort to practice what I preach about being active on this forum, here is a topic of discussion that some of you might want to offer commentary:

Last week’s seismic event in Venezuela was initially confusing for me, and to a number of seismologists around the world, due to the announcement of two earthquakes of magnitude 7.2 and 7.5, when the raw data made it appear as though there was a single event. It wasn’t until some colleagues at GA sent me this link that showed how USGS determined the two events using a technique called Back Projection. If you look at the data from the NA (North American) network, the two energy releases are most obvious.

How does this type of event sequence figure into design for earthquake engineering? The two earthquakes were only separated by 40 seconds, so the energy waves would have overlapped, making the earthquake shake longer than either of the events would have individually. This means more cycles, and potential amplification of energy waves at harmonic frequencies.

This doublet had different dynamics to the doublet in Türkiye from a few years ago - those were separated by hours, so already damaged buildings had to endure a second round of extended shaking, so it’s hard to compare the effects of these two scenarios that have some similarities but also a lot of differences.

I was also wondering how earthquakes like these that trigger earthquakes on nearby faults differ from earthquakes like Kaikōura that also rupture along multiple faults. In the latter case, the rupture is a continuous event along fault structures, jumping from one nearby fault to the next, whereas with Venezuela the energy waves had passed, but brought a locked section of another fault to failure, initiating a second energy release.

As someone who is only used to looking at relatively small local earthquakes and doesn’t have much experience with fault dynamics, I’m still learning and trying to understand how the various scenarios work. I’m assuming there are other AEES members that probably also aren’t aware of how these events can play out, so I just thought I’d share what I’ve learnt in the last week. If anyone has further insights to share, please do.

In the end, all of this is matters little to how this event is affecting the people of Venezuela, who are suffering terribly in the ongoing recovery process. Our thoughts are with them, and I hope that when they rebuild their cities there will be adequate consideration for earthquake engineering in the design of their new infrastructure.

Adam Pascale

Chief Scientist

Seismology Research Centre

Find me on Bluesky, Instagram, TikTok and LinkedIn

[geor...@bigpond.net.au]

Adam

 

I presume you are aware that NZSEE has already produced a Virtual Report of the earthquake prepared by a group of members extracting material online from various sources.  It appears to have quite a detailed section on the seismology of the event.

 

George Walker

 

George & Mary Walker

229/96 Village Way

Little Mountain Qld 4551

Australia

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[Wayne Peck]

Thanks for kicking off the discussion Adam and thank you for the mention of the NZSEE report George, I had not seen that.

I'm curious how we can reasonably incorporate doublet type events into PSHA. Standard practice in terms of the hazard catalogue would be to decluster the catalogue and presumably remove the foreshock in order to preserve the Poissonian assumption of event independence. Of course we've long known that assumption is a fiction for earthquakes and there are proponents of the use of non-declustered catalogues. This is possibly leading into the area of time dependant PSHA which I don't know much about but would love to hear any input that others may have.

 

Wayne Peck

Operations Manager, Seismology Research Centre

141 Palmer Street, Richmond VIC 3121, Australia

M +61 4 1932 3505 T +61 3 8420 8942 

Find us on our Website, LinkedIn and YouTube

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[Simon Matthews]

Dear All,

I would like to shear an article from The New York Times on how Android  phones provide some alert to these EQ's.

[Jordan Bartlett]

Are you shearing again?

 

You kiwis and your shearing… sheep or walls?

 

I’ve hear you don’t share your sheep with anyone.

 

Love your work mate 😊 and hopefully my joke is okay

 

JB

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[Somerville, Paul]

G’day

 

See attached note and video of directivity pulse collapsing a building at the same time people are thrown down to the ground.

The ground motion becomes visible at about 1 minute 25 seconds into the video, and lasts about 7 seconds.

 

https://www.youtube.com/watch?v=jCZgv7fLJmY

 

The attached paper explains how the forward directivity pulse is generated

 

Paul

 

Principal Seismologist

AECOM

300 South Grand Avenue Suite 900

Los Angeles, CA 90071

Paul.so...@aecom.com

Cell (626) 200 5231

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[Jordan Bartlett]

Apologies all, I’ve fallen into the trap oif thinking I was writing privately to Simon… My error.

 

I hope you all have a great weekend and can forgive me.

 

Jordan

 

From: aee...@googlegroups.com <aee...@googlegroups.com> On Behalf Of Jordan Bartlett

Sent: Saturday, 4 July 2026 12:41 PM
To: aee...@googlegroups.com

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[Kevin McCue]

Thanks Paul, rather shocking how brittle that building was. 

Were there any strong motion instruments in the areas of high damage along the fault? or any at all?

There was no attached file, just the video. 

Cheers

Kevin

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Kevin McCue
Director
Australian Seismological Centre
Canberra ACT
Australia

[James Daniell]

Thanks for sending through Paul. Very interesting! I am running the GRADE assessment for the event. We have been trying through Funvisis and all contacts possible to get at any strong motion data, however it is impossible to find, and apparently there is some but also has been classed as sensitive by the govt! Thus we are currently going backwards from the individual building damage and back calculations to the possible spectra. Is a complex one with the site effects as well though and building deficiencies.   If anyone has any strong motion data would love to bring it in as we are not going to have a full damage picture before from the govt and the AI-Satellite damage proxy maps etc are all over the place in terms of their quality.

Greetings from Germany to all (after getting back from the 18m high Lava barriers around Grindavik in Iceland).

Cheers,

James.

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[bill boyce]

Dear all,

"Our thoughts are with them, and I hope that when they rebuild their cities there will be adequate consideration for earthquake engineering in the design of their new infrastructure.”

One of the many documents I read when I began my studies in earthquake engineering in Papua New Guinea in 1968 was the report on the Venezuela Earthquake July 29 1967, published in 1969 by the American Iron and Steel Institute.The seismic provisions of the Venezuela Standard for Building Design-1955 were strengthened after that earthquake and possibly have been improved many times in the past 60 years.

An interesting exercise would be to study building performance in relation to the earthquake standard in force at the time each structure was designed and built, to see if improved standards (on paper) have made any difference to the performance of the built structure.

The AISI report contains a chapter titled “Lessons learned and relearned.” I suspect that with minor editing the same chapter would fit well in any report on the 2026 earthquake.

Regards

Bill Boyce

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[Somerville, Paul]

G’day

 

This is the Funvisis website listing the strong motion network but there is no indication of how to access strong motion records,

which James has been trying to do without success so far.

 

http://www.funvisis.gob.ve/old/red_acelerografica.php

 

I expect that the ground motions were lower than average for a magnitude 7.5 strike-slip earthquake because the rupture

velocity was only about 2.2 km/sec and the average fault displacement was only about 1m, but the rupture directivity pulse

could still be quite strong because it represents the summation of the ground motions generated from the whole fault

rupture up to that point.

 

Paul

 

Principal Seismologist

AECOM

300 South Grand Avenue Suite 900

Los Angeles, CA 90071

Paul.so...@aecom.com

Cell (626) 200 5231

 

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