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:
Take a break from your too-serious-work
Open the folder with all the field photos
Choose the best/funniest/strangest ones
Smile
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.
Besides the classical paleoseismology studies in today’s list, we have some papers that deal with secondary and cascading effects of earthquakes, such as landslides and diseases, and interesting new findings on short term and long-term tectonic geomorphology. Enjoy reading!
Project EDITH runs under the umbrella of INQUA’s TERPRO commission and the Int’l Focus Group TPPT (Terrestrial Processes Perturbed by Tectonics). EDITH proposes to organize and facilitate annual meetings with a wide range of experts in earthquake geology, paleoseismology, geodesy and tectonic geomorphology to gain a better understanding of the earthquake cycle with the final aim to provide constraints for future new seismic hazard assessment (SHA) geologically-based models. The kickoff meeting has now been scheduled to 14-16 April, 2021 and will be held via Zoom.
On 23 June, 2020, a magnitude 7.4 subduction earthquake struck western Mexico and let the earthquake early warning sirens sound in the capital. Reportedly, ten people lost their lives and thousands of houses were damaged in Oaxaca. Our colleagues Magda Velázquez-Bucio, Sabina Porfido, and Alessandro Michetti have put together a report on the Earthquake Environmental Effects of this event in English and Spanish:
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).
It is with great sadness that we received note from the passing of our dear colleague Victor Hugo Gorduño Monroy.
Victor was a close friend to many of us and an outstanding person in the Mexican scientific community. He authored a great number of publications on the geology of Mexico, on tectonics, volcanism, and hazards. His work did not only advance geosciences, but also had huge impact on society. He was tireless in helping to raise the awareness for disasters and to promote geoscience in the public. We will never forget his enthusiasm and his dedication in the field.
He had the leading role in geosciences at the Michoacan University of San Nicolás de Hidalgo and taught hundreds of students during his career.
Victor organized the first PATA days outside Europe in November 2012 in Morelia in commemoration of the 1912 Acambay Earthquake, which was an absolute pleasure and a great success.
Our thoughts are with his family and with everyone who worked closely with him.
The Michoacan University of San Nicolás de Hidalgo released the following letter of condolence:
El día de hoy sufrimos la pérdida de una de nuestras más sólidas columnas institucionales. Informamos con profunda tristeza que el Dr. Víctor Hugo Garduño Monroy falleció esta mañana y con él perdimos a nuestro Líder Académico y Fundador de la Maestría en Geociencias y Planificación del Territorio y del Instituto de Investigaciones en Ciencias de la Tierra. El Dr. Garduño fue un incansable investigador de la Geología de nuestro Estado y del Occidente de México. Formador profesional de centenares de estudiantes a nivel profesional y posgrado. Ganador de la Presea José María Morelos y Pavón y Primer Investigador en Obtener la Presea Vasco de Quiroga en nuestra querida Universidad Michoacana de San Nicolás de Hidalgo. Hoy se fue uno de los mejores investigadores de nuestra Universidad, de nuestro Estado y de nuestro País. Siempre será recordado por el cariño a su profesión, a sus estudiantes y compañeros. Descanse en Paz.
Victor (right) with his friends and colleagues during the 2012 PATA Days in Morelia, Mexico.
Moderate to
strong earthquakes commonly produce secondary effects (landslides,
liquefaction, tsunamis), which worsen the impact of the seismic event, both during
the emergency and recovery phases.
Landslides
can be triggered by events of M above 5 or so, and stronger events can produce
thousands of landslides. Landslide inventories were compiled for dozens of
events and the relations between Mw and maximum distance or area affected by
landslides have been analyzed (e.g., Keefer, 1984; Rodriguez et al., 1999). On
the other hand, the total area affected by landslides is one of the metrics
used to assign the ESI intensity (Environmental Seismic Intensity; Michetti et
al., 2007).
The Hokudan 2020 International Symposium on Active Faulting will take place from 13-17 January in Awaji City, Awaji Island, Japan. The symposium is held every five years. The 2020 event commemorates the 25th anniversary of the 1995 Kobe earthquake. All important information on this meeting is available here: https://home.hiroshima-u.ac.jp/kojiok/hokudan2020.html
This event is supported by INQUA – the International Union for Quaternary Research and its TERPRO commission. For more information, please contact Koji Okumura (kojiok@hiroshima-u.ac.jp) or Shinji Toda (toda@irides.tohoku.ac.jp).
On July 4th and 5th, 2019 two earthquakes (Mw 6.4 and Mw 7.1, respectively) occurred in eastern California and produced distinct surface ruptures. Field surveys started immediately after the first event and, less than two weeks later, a provisional map of surface rupture was compiled and made available to everyone (Contributors from USGS, CGS, UNR, USC, CSUF). I downloaded the map and kmz files of the ruptures from the SCEC response site, which contains tons of fruitful information.
The two strike-slip earthquakes ruptured two perpendicular faults, the first running NE-SW with left-lateral slip and the second running NW-SE with right-lateral slip (Figure 1). The location of the earthquake falls within the Eastern California shear zone, a region of distributed faulting associated with motion across the Pacific-North America plate boundary, and an area of high seismic hazard.
Figure 1. Left: ground breaks caused by the 2 earthquakes. Right: simplified trace, used as main fault.
Ruptures come
with a variable degree of complexity: some sectors show a “simple” single
strand, others show multiple sub-parallel or diverging splays. Distributed
faulting represents displacements occurred off the principal fault and is
generally made up by less continuous ruptures, which can be located tens of
meters to a few kilometers from the principal fault trace. A method to evaluate
the fault displacement hazard has been proposed by Youngs et al. (2003) and
later refined by Petersen et al. (2011); the former study analyzed normal
faults, while the latter analyzed strike-slip faults.
Basically,
the method defines the conditional probability of faulting occurrence as a
function of distance from the principal fault and derives scaling relations
between rupture probability and distance. I applied the same method on the 2019
sequence and compared the output with the results by Petersen; results are
grid-dependent – since available data are still provisional, I used a quite
coarse grid size of 200 m, more detailed studies will come.
Results are in good agreement (Figure 2): the 2019 ruptures show a higher than average rupture probability at 0-2 km from the main fault, but also taper out faster than the previous events.
Figure 2. Comparison between the 2019 events (blue: July 4th; red: July 5th) and data by Petersen et al. (empty circles). The probability of occurrence of faulting is plotted as a function of distance from the main fault (left: linear horizontal axis; right: logarithmic scale).
References:
Petersen, M.
D., et al. (2011). Fault displacement hazard for strike-slip faults. BSSA,
101(2), 805-825.
Youngs, R.
R., et al. (2003). A methodology for probabilistic fault displacement hazard
analysis (PFDHA). Earthquake Spectra, 19(1), 191-219.
