Francesca Ferrario

The year 2023 saw devastating earthquakes occurred in Turkey-Syria and Morocco, which caused thousands of victims and heavy destruction. This post is going to have an ironic tone, but we should not forget that our duty as paleoseismologists is to provide to policymakers and society the means to take the best informed decisions.

Usually, we do it by digging paleoseismic trenches and analyzing what they uncover. The 2023 trenchiest trench picture was posted on X (former Twitter) by Gülsen Uçarkuş, showing their trench cut into half by surface faulting following the Turkey-Syria earthquakes.

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Trench with a view

Paleoseismology can bring you to wonderful places:

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The devil is in detail

By simply looking at pictures, one can learn a ton from different styles and habits. And discover unusual expedients.

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Shapes

Trenches come in all sorts of sizes and shapes:

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Trench mindfulness

Trenching team mandatory equipment: foldable chair or any other object suitable for sitting on it and sketching the trench log.

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Holy cow! (and other animals)

If only the students attending my lessons were interested in my slides like these animals are in trenches…

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Not surprising that cows are supervising trench excavations.

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Excavator operator shout-outs

They are often underappreciated but are a fundamental component for a good result!

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Hand-dug trenches shout-outs

For the bravest only:

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No caption

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If you enjoyed this post, don’t buy me a coffee – I’m already caffeine-addicted. On the contrary, please go and make your workplace a better one: be kind to your peers, don’t put pressure on the students you’re supervising or don’t stress the hell out of your supervisor!

TERPRO’s project EDITH (From Earthquake Deformation to SHA) is organizing its meeting for the 13th -16th November 2023 in Israel.

Please visit this website for further information, registration and abstract submission:
The abstract submission deadline is Sept. 30th 2023.
Hurry up and register! 😉 presently there are still many seats available, but there is room for 50 people only.

The organizers are waiting for your contribution for one of the 5 scheduled scientific sessions. See the detailed program here

Hey paleoseismicity nerds!

At the wonderful Inqua meeting in Rome I saw plenty of presentations and posters with trench pictures. After the first edition in 2022, it’s time to look for the trenchiest trench pictures of 2023. Here’s what you need to do:

1. Take a break from your too-serious-work
2. Open the folder with all the field photos
3. Choose the best/funniest/strangest ones
4. Smile
5. Post them on Twitter and tag @GingerFault or send me an email since the bird app is quickly agonizing.

This year categories include “trench with a view”, “the devil is in detail”, “holy cow!”, “trench mindfulness” plus other random stuff which I cannot reveal right now since I still have to figure them out.

A new paper has been recently published in Quaternary International, summarizing the “New developments in onshore paleoseismic methods, and their impact on Quaternary tectonic studies”.

The paper is the result of a cooperative effort (12 authors from 6 different countries and 3 continents) led by Jim McCalpin. Sorry for the paywall, feel free to contact me or the other authors – we will be more than happy to share our work!

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The Aix-en-Provence PATA Days are fast approaching and the meeting programme looks super-exciting! Unfortunately, I’ll not attend the congress, but my soul will be there in poster form – presenting author is 1^st year PhD student Marco Pizza and the topic is the likelihood of primary surface faulting.

Some earthquakes produce surface faulting, others do not. Several factors affect the outcome of this dichotomous variable (faulting YES/NO), including magnitude, depth, earthquake kinematic and local lithology. The probability of having surface rupture for a given magnitude is a key ingredient in Fault Displacement Hazard Assessment (FDHA). This probability is derived from empirical datasets and the state of the art is summarized in Figure 1, taken from the recently published IAEA Tecdoc on probabilistic FDHA.

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The XXI Inqua congress will take place in Rome in July 2023. Don’t forget to submit your abstract, deadline is November 1st, 2022! Submit your abstract here

Below are some highlights on sessions centered on earthquakes, active faulting and tectonic stuff, but remember to check the full list – 209 proposed sessions!

Keep on reading!

Following an un-systematic post-dinner doomscrolling I’m happy to declare May 2022 as the trenchiest month ever. Here’s some exhibits:

Safety first; if cozy and comfy it’s better.

The award goes to Stéphane Baize (@Stef_EQ_Geology) and their trenches along the Cévennes fault: look at the details in the photo… like “paleo” engraved in the wooden frame to prevent collapse of the trench wall. And what about the tent? 10/10 professional style.

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Landscape photography award

The winner is Colca Canyon in Southern Peru, take a look at the pictures by Anderson Palomino (@AndersonRPT1) and Carlos Benavente (@clbenavente)

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Best flower structure award

No doubts here, easy win for Ian Pierce (@neotectonic) and their trenches in Azerbaijan. Follow him for stunning field photos and videos.

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Mud club

Mention goes to Jade Humprey (@ForFaultsSake).

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The tricks of the trade.

Learn them from Jonathan Obrist-Farner (@guateologist) uncovering the mysteries of the 1976 Motagua rupture in Guatemala

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Category “You don’t need a trench to find good stratigraphy”.

Prize goes to Gabriel Easton Vargas (@geastonvargas) and paleotsunami research in semiarid Chile

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Category “Let’s the student do the work”.

Terrific exhibit by Shreya Arora (@shryaarora) trenching in the Himalaya region

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Never without a nijiri gama.

Award is won by Sambit Prasanajit (@SPrasanajit) and their sites in S. Korea

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Fancy fence

The winner is PhD student Argelia Silva Fragoso (@Argy_sf) from Insubria university, digging trenches in Central Italy

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Sorry if I missed someone, I wish you all a safe and fruitful field season!

Five years ago, on October 30, 2016, a Mw 6.5 earthquake nucleated along the Vettore Fault in Central Italy.

This event is particularly interesting because its surface rupture overprinted the faulting occurred only 3 months earlier, on August 24. In the last 5 years, at least 2 other cases of repeated rupture in a short time interval were observed, i.e., the 2016 Kumamoto (Japan) and 2019 Ridgecrest (US) sequences.

Fault re-ruptures are currently not accounted for in seismic hazard assessment; should paleoseismology folks care about re-ruptures? To answer this question, it is necessary to understand how common re-ruptures are.

So, I checked the USGS catalogue, looking for earthquakes with M > 6, depth < 30 km occurred since January 1^st, 2016. I chose these thresholds because I’m interested in surface-rupturing events, but maybe the values need some fine-tuning. The search returns 490 earthquakes. Then, I filter out events with epicenters offshore, since surface faulting is more difficult to document there. A total of 104 earthquakes (21% of the total) occurred onshore (Figure 1).

Figure 2a shows the distribution of the 104 earthquakes according to magnitude (bin size 0,2 magnitude units). Now I calculate the expected number of surface-rupturing events, using the probability curves provided by Youngs et al. (2003; their Equation 4) and shown in Figure 2b. Out of the 104 earthquakes, it can be expected that 63 should have produced surface faulting.

Finally, let’s check how many re-ruptures have been actually observed: as mentioned earlier, they are at least Kumamoto, Ridgecrest and Central Italy. Three out of 63 means that ca. 5% of the shallow M > 6 earthquakes onshore include the repeated rupture of the same fault strand(s).

This has strong implications for paleoseismology, because it is virtually impossible to identify events occurring few months or years apart. In turn, this may affect the computation of key parameters for seismic hazard assessment, such as recurrence interval, slip per event and elapsed time.

These ideas are at the core of a project I’m writing right now, called REDEFINE: “RE” stands for re-rupture and Task 1.1.3 will be the update of the probability curves of Figure 2b – no more spoiler on the project!

If I’ll get that 1 million €, you’ll hear more on re-ruptures from me 😊

 

 

 

While working on my project on distributed faulting, I dig into the literature looking for additional case studies beside those contained in the SURE (SUrface Ruptures due to Earthquakes) database.

I retrieved information on 18 normal and strike-slip events occurred between 1905 and 2011, with a magnitude range of Mw 5.9 – 8.3. I digitized rupture traces from published maps at a variable scale, dependent on the resolution of the original map. Earthquakes are from Iran (7 events), Mongolia, China, Turkey, Greece (2 events for each country), Italy, Kenya and Japan (1 event).

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The recent publication of a paper on the Weitin Thrust (Papua New Guinea) by Chen, Milliner and Avouac (Fig. 1) gave me the opportunity to dig out and look back to some notes I wrote few months ago. Chen et al. use optical image correlation to document coseismic surface ruptures along the Weitin Thrust occurred in a Mw 8.0 event in 2000 and in a Mw 7.7 event in 2019. The ruptures overlap along a 20-km long portion, with 3-4 m of slip (Fig. 2).

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