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. Continue reading “Guest blog: “Photogrammetry for Paleoseismic Trenching” by Nadine Reitman (USGS)”
Just a friendly reminder that the deadline for abstract submission for the EGU general assembly 2016 in Vienna is tomorrow, January 13th at 13:00 CET/12:00 GMT. If you are still looking for a session to submit your abstract to, please have a look at our session about Active Faults and the Earthquake Cycle (TS4.2/NH4.16/SM3.8)
By the way, the Vienna Basin is the perfect place to discuss active faults, as you see on our newest gravel pit outcrop. If you interested in having a closer look at this fault during the EGU – let me know…
Hopefully see you soon in Vienna,
Esther, Kris, Matthieu, Angela
Continue reading “EGU deadline tomorrow”
The first part of my report on the field work that I did in Kazakhstan this year focussed on the stuff we had done in the South. Here is part II which is all about the Dzhungarian Fault. You’ve never heard about this fault? That’s easily possible. There are only very few papers that deal with this fault. In the 1960s Soviet geologist V.S. Voytovich published results from extensive field work on this fault (Voytovich, 1965; 1969). 40-50 years later a few studies on geodesy and geodynamics covered the broader study area and Shen et al. (2003) did some work in the Chinese part of the fault, but it took until 2013 before Campbell et al. revisited the Kazakh side and came up with new field data. They focussed on the tectonic geomorphology of this structure and determined a slip rate. Given this little amount of research done one would assume that the fault is not very large and of minor importance, but the opposite is true. The fault is around 300 km long in its Kazakh section and probably twice as long in total! Continue reading “This was my field work on active faults in Kazakhstan 2015 (pt. II)”
I’ve spent several weeks in Eastern Kazakhstan this summer for paleoseismological field work. During the first part of this trip we looked at some thrust and strike-slip faults in the Ili Basin and the Saty area. The second part was almost entirely devoted to study the Dzhungarian Fault. I’ll blog about this second part later. Eleanor, David, Austin and me were the UK representatives in our team. We were so lucky to have Kanatbek from Kyrgyzstan and Aydin from Kazakhstan with us. They did not only lead us to all the interesting places and helped us to understand the geology and the tectonics, but they also did a fanatastic job organizing the field trip and dealing with the local surprises, which as you know happen in basically every field trip.
Our first study site was located at the northern boundary of the Ili Basin, where we did some work last year already. Continue reading “This was my field work on active faults in Kazakhstan 2015 (pt. I)”
The Canyonlands National Park, Utah, is famous for its beautiful landscape and spectacular landforms. For many geoscientists it is also well-known as a sandstone reservoir analogue and as a tourist you’ll often run into groups of geologists on field trips. It’s a matter of debate how and how fast the beautiful grabens in the Needles Fault zone formed – these are large arcuate canyons several tens of kilometres in length, paralleling the Colorado River. In a new paper we present results from remote sensing, mapping, and georadar (GPR). Our aim was to better understand the coupling between deformation, erosion and deposition in such an active system. Based on our findings we developed a model of graben formation and describe the geometry of the dilatant faults at depth. We argue that either the grabens are older than previously assumed or that sedimentation rates were much higher in the Pleistocene.
Continue reading “New paper: Evolution of dilatant faults in the Canyonlands NP, Utah”
A few weeks ago I spent ten days of field work in the Suusamyr Valley in Kyrgyzstan. In the framework of the EwF Project and COMET a team from Oxford (Eleanor Ainscoe, Austin Elliott, Richard Walker) and Kyrgyzstan (Kanatbek Abdrakhmatov, Azat Moldobaev) re-visited the epicentral area of the 1992 MS7.3 Suusamyr earthquake. This thrust earthquake is quite special for it produced intense and widespread secondary earthquake environmental effects (landslides, rockfalls, secondary ruptures, mud eruptions, etc.), but remarkably short primary surface ruptures only. Actually, surface ruptures of several metres height were found near the Suusamyr river, but limited to few hundreds of metres in length. Some 25 km to the west, another set of surface ruptures appeared, which were only about 1 m in height and less than 3 km long. Here are some impressions from our field work. Continue reading “Paleoseismological field work in Kyrgyzstan”
The Megablock Complex: An example from the East African Rift
Recognizing and interpreting seismite horizons (soft-sediment deformation generated by earthquakes) preserved in the sedimentary record is an underappreciated approach for paleoseismic analysis. The addition of sedimentological studies to a toolkit that includes other well-established methods, such as instrumental seismic monitoring and fault trenching, can provide a less expensive and more practical option for earthquake hazard prediction and preparation in certain areas. For example, this may be a good option in less developed regions and in areas where fault trenching may not be possible. Moreover, there is a lot that we can learn rheologically from the study of seismites that could be invaluable for modeling the behavior of the surface/near-surface during seismic activity. Similarly, investigating Quaternary strata in areas that may be prone to seismicity, which may or may not have a recorded history of major earthquakes, can illuminate important information about earthquake recurrence patterns and intervals, in much the same way as fault trenching. Continue reading “Paleoseismology Through Sedimentology”
Last Friday the RAS held a discussion meeting on Tectonics from Above: Recent Advances in the Use of High-resolution Topography and Imagery in London. Almost the entire Cambridge Tectonics Group went there and I absolutely enjoyed the meeting and the discussion with friends and colleagues mainly from the UK and from France. The speakers reported on open-source software for producing high-res DEMs, advances in aerial and satellite imagery, new techniques in remote sensing, and latest developments in fault/offset mapping. The meeting was supported by NERC, COMET+ and LICS. Continue reading “Tectonics from above – RAS discussion meeting”
“Blown in the wind” Bob Dylan would have said or, at least, by. An international team (Università dell’Insubria, Università degli Studi di Milano – ITALY, Universität Innsbruck – AUSTRIA) found evidence of surface secondary faulting by blind thrust thanks to a promising setting characterized by syn-growth aeolian sedimentation, at the northern fringe of the Po Plain (N Italy). Results were published this year, in the Journal of Geophysical Research.
Continue reading “Surface compressive deformation constrained through a Loess/paleosol sequence: a case study from northern Italy”
Our latest paper on coastal change in Oman deals with an extreme flood event that was recorded in an archaeological site in Ras al Hadd, at the easternmost tip of the Arabian Peninsula. We found multiple evidence for tsunamis that hit Oman’s coast in the past. Close to Fins, mega-boulders were thrown on a cliff by huge waves. Fine-grained sediments typical for tsunami action were found in the same area. Searching for further evidence, we came across the archaeological site of HD6 in Ras al Hadd. The archaeologists who were excavating this site told us about strange findings in the archaeological record – they encountered a layer that interrupted the otherwise continuous stratigraphy of the settlement. The bronze age fishing village is located very close to the coast only a few meters above sea level, a large tsunami could easily impact here. Continue reading “New paper: How archaeology records extreme flood events in Oman”