Happy New Year everyone! May 2022 bring you health and joy, and may you always encounter nice reviewers and great outcrops. Enjoy reading our latest selection of active tectonics & paleoseismology papers.

Soft-sediment deformation structures are often used as evidence for paleo-earthquakes. When several deformed horizons are present, one has to ask whether repeated slope failure at the sediment surface has built-up the stratigraphic record. Another option would be that a single failure event could have concurrently created surficial and sub-surface deformed horizons at different stratigraphic levels. The implications of these differing models are important for the timing of palaeo-earthquakes. In a new paper, Alsop et al. used the late Pleistocene Lisan Formation from the Dead Sea Basin to catalogue and establish key criteria that help distinguish surface versus sub-surface intrastratal deformation of soft-sediments. The paper is available for free for 50 days!

It’s already December and 2021 is finally coming to an end – although it felt like two years. Anyway, here’s the last list of papers for this year. It includes a great review article on paleoseismology and a new IAEA tecdoc for surface displacement hazard. Plus, lots of cool other studies. Enjoy reading!

We are happy to announce that the organization of the PATA Days in France has progressed: the conference will occur during the last week of September 2022, i.e. from 26^th (Monday) to 30^th (Friday). Save the dates! PATA stands for Paleoseismology, Active Tectonics, Archaeoseismology and is supported by INQUA‘s TERPRO commission. Learn more about the history of the PATA Days here.

The venue and further details will be fixed in the upcoming weeks. Also, registration is not possible yet. Meanwhile, have a look at the website with info on the programme, the scientific sessions, and the planned excursions: pata-days.org.
See you all in France!

The South Caspian Basin (SCB) is an aseismic block that moves independently to its surroundings. Together with the Arabia-Eurasia collision, it controls the active tectonics of Turkmenistan. The directions, rates, and rotation poles of the SCB relative to Iran and Eurasia are not well resolved. In a new paper recently published in TECTONICS, we constrain the motion of the SCB by measuring the slip rate of the Main Kopeh Dagh Fault (MKDF) in Turkmenistan. Here’s what we found:

A new special issue has been published in Frontiers. While most of paleoseismological studies deal with onshore faults for obvious reasons, this collection of 15 studies is all about offshore faults. The papers are of course full of wonderful high-resolution bathymetry data and shallow seismic profiles, but they also deal with the important question of how to implement these data into seismic hazard assessments and how to deal with the patchy fault information. The study areas cover marine settings and lacustrine environments.

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 😊

This months we have a lot of studies on Mediterranean tectonics, first of all from Italy, and many papers on China and the US. Besides, there are some interesting methodological studies and research from areas that had recent seismic crises such as Puerto Rico and Thessaly. Enjoy reading!

A new Special Issue has just been published in the Journal of South American Earth Sciences: Hazardous Faults in Latin America. The issue contains 16 research papers and an editorial. It was edited by Carlos Costa and Laurence Audin. The issue collects highly interesting contributions from all across the continent. Although subduction megaquakes on the Chilean Trench come with the highest magnitudes, onshore faults pose a significant hazard and historical events have had catastrophic consequences. Also, studying crustal earthquakes and faults is a pre-requisite for understanding crustal deformation, mountain building, and the landscape response to tectonics. Read the Special Issue now, because all papers are free to access via ScienceDirect until 20 Jan 2022.

A new special issue has been published in MDPI’s Geosciences. The collection “New Perspectives in the Definition/Evaluation of Seismic Hazard through Analysis of the Environmental Effects Induced by Earthquakes” collects five review papers, 13 research articles, and an editorial. The SI was edited by Sabina Porfido, Giuliana Alessio, Germana Gaudiosi, and Rosa Nappi. The volume is also available as a book. Download the flyer as a pdf here.