Posts in the category »  Field work «  ( 30 Posts )

[UPDATE 2017-05-14: The links now lead to the free version of the paper, available until 30 June.]

Together with my colleagues I have published a new paper in which we describe a methodology for mapping the shallow architecture of large sedimentary basins with minimum effort and high resolution. We use two geophysical methods and combine them with point information from shallow drillings to identify different types of alluvial, fluvial, and aeolian sediments in the Orkhon Valley in Mongolia. We then show that our results fit well with a remote sensing approach. Although we did not target active faults in our study, the methodology is well suitable for detecting deformed/offset sediments without surface expression due to high erosion or sedimentation rates. That’s why I feel the study is of interest for the fault-hunting community. more

The city of Cusco in Perú has been hit by damaging earthquakes several times in its long history. In Inka times a strong earthquake destroyed parts of the city, and the Spanish invaders documented an earthquake that happened in 1650. Three hundred years later, in 1950, an earthquake destroyed large parts of modern Cusco and in 1986 a M6.1 event also led to damages in the city. In order to better understand the active normal faulting in the region, INGEMMET has launched the project Cusco-PATA (Paleoseismology, Archaeoseismology and Active Tectonics – “pata” also means “scarp” in Quechua). The project brings together scientists from Perú, Spain, France, and the UK. The 2017 field campaign started in mid-April with work on the archaeological sites in and around Cusco and paleoseismological trenching of the Pachatusan Fault. more

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The Chilik-Chon Kemin Fault Zone is a major left-lateral strike-slip fault zone in Kazakhstan and Kyrgyzstan, just a few tens of kilometres east of Almaty and north of Lake Issyk Kul. It has seen one of the largest continental earthquakes ever recorded in 1889, with an estimated magnitude of ~M8.3. In July and August I had the chance to visit this fault zone for two weeks together with Angela Landgraf from Potsdam and Aidyn Mukambaev from the National Data Centre, thanks to a travel grant from COMET (thanks so much, COMET!) and with support from the EwF Project. We wanted to find out more details about the tectonic geomorphology of this fault zone and we wanted to study the slip rate and earthquake recurrence intervals. So we took our drone, shovels and picks and set off for a field trip into the mountainous wilderness. Since I will leave for another field trip to Kazakhstan (Dzhungarian Fault) tomorrow, I will leave you with some impressions from our field work and provide more information once the paper is published…
Enjoy!  more

Ruptured pebbles are frequently found near and along active faults. At RWTH Aachen University Christopher Weismüller has just finished his MSc thesis on ruptured pebbles in southern Spain. There, the NE-SW trending Carboneras Fault System meets the N-S trending Palomares Fault and ends. more

The geometry, length, and displacement of fault ruptures that breach the surface provide critical information on the behavior of faults during seismic events (coseismic deformation), and on their long-term behavior. The study of coseismic fault ruptures has concentrated almost exclusively along continental faults, while submarine studies have been scarce, and only a few provided quantitative constraints in parameters such as fault displacement (e.g., Tohoku Earthquake). In addition to represent more than two thirds of the Earth’s seismicity, submarine faults can also be associated with tsunamis, potentially increasing the seismic hazard that these structures pose.

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Between 1885 and 1938, the northern Tien Shan at the border between present Kyrgyzstan and Kazakhstan experienced a remarkable series of five major earthquakes, exceeding M6.9 and reaching up to M ~ 8 (1885 Belovodskoe M6.9, 1887 Verny M7.3, 1889 Chilik M~8, 1911 Chon Kemin M8, and 1938 Kemino Chu M6.9). Combined, the seismic moments add up to almost moment magnitude 9, which is a significant amount of strain released in roughly 50 years and across an E-W stretch of less than 500 kilometers. Even more intriguing is the fact that the ruptured region is located more than thousand km north of the nearest plate boundary and associated India-Eurasia collision zone. The macroseismic areas of these earthquakes include the present-day capital of Kyrgyzstan, Bishkek (Frunze) and the former capital and still largest city of Kazakhstan, Almaty (earlier names Alma Ata and Verny).
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[Update 15 February 2017: Since Sascha is an author here now, the post was attributed to him.]
Greece is one of the main targets of RWTH Aachen’s Neotectonics & Geohazards group. They worked on paleo-tsunamis, active faults on the Peloponnese, in Attica, and on Crete, and on the application of terrestrial LiDAR and shallow geophysics for active tectonics research. In their latest paper, Sascha Schneiderwind et al. developed a methodology to aid paleoseismic trenching studies. They use t-LiDAR and georadar to better and more objectively characterise lithological units. His paper includes nice examples from Crete and from the famous Kaparelli Fault. Here is his guest blog: more

Tsunamis are a very real threat in the Indian Ocean. Most people will immediately think of the 2004 tsunami and the Sumatra subduction zone, but the Arabian Sea has seen strong tsunamis in the past, too. In 1945, a major earthquake at the Makran Subduction Zone caused a large tsunami (Hoffmann et al., 2013a). In 2013, the on-shore Balochistan earthquake caused a submarine slide which in turn triggered a tsunami that reached the coast of Oman (Heidarzadeh & Satake, 2014; Hoffmann et al., 2014a). There is also evidence for paleotsunamis along Oman’s coast (Hoffmann et al., 2013b; Hoffmann et al., 2014b). Now a team of scientists from RWTH Aachen University (Germany) and GUtech (Muscat, Oman) have published a tsunami inundation scenario for Muscat (Schneider et al., 2016). This is lead author Bastian Schneider’s guest blog on this research: more

A few weeks ago, Nadine Reitman (USGS) published an interesting paper about the use of Photogrammetry for Paleoseismic Trenching in BSSA. In this guest blog she shares her key findings and explains how to minimise errors without spending too much time measuring control points. Thanks Nadine!

Structure-from-motion (SfM) is now routinely used to construct orthophotos and high-resolution, 3D topographic models of geologic field sites. Here, we turn SfM on its side and use it to construct photomosaics and 3D models of paleoseismic trench exposures. Our results include a workflow for the semi-automated creation of seamless, high resolution photomosaics designed for rapid implementation in a field setting and a new error analysis of SfM models. more