Category Archives: faults

Active Tectonics of the Andes (ATA) active fault database now on GitHub

In order to facilitate collaboration in development of the Active Tectonics of the Andes (ATA), a database of active faults in the (northern, for now) Andes, we have hosted it on GitHub.  The development version is here, although the ‘release’ versions will continue to be posted on the KU HawkDrive, as before.  We have received some comments about incompleteness of the 1.0 version in certain areas (such as around Quito, Ecuador), and we used that information to expand the database in those areas.  The database is now at the 1.1 version, as well.  All New and Improved!

I would also happily field other requests for improvements in the database both geological (such as about specific faults or regions) and technical (new file formats, etc.).  Please, don’t hold back!  This is a free, public, open-source project and the more minds we have working on it, the better the database will be.  And as this database improves, so does knowledge of structures responsible for seismic hazard to communities in South America.

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Article on the South Lunggar rift, western Tibet, accepted in Tectonics

A big part of my PhD was the exploration of a large, but essentially unknown, active rift in southwest Tibet, the South Lunggar rift.  We mapped the rift, and did a solid amount of zircon (U-Th)/He thermochronology, combined with thermal modeling using Pecube, and did some ancillary zircon U-Pb geochronology as well.

The rift itself is a central horst bound by two rift basins, with major, active normal faults between the horst and the rift.  Structural and thermal observations and modeling suggest a total of 10-21 km extension since ~10-12 Ma, at modern rates of ~1-3 mm/yr.  There is pretty good evidence for an rapid increase in extension rate at 8 Ma, on the most significant fault in the rift, the low-angle South Lunggar Detachment.

We have just gotten a paper accepted in Tectonics that covers most of what is known about the rift.  The official Tectonics page is here, although the PDF that they host has some serious formatting errors and the figures are atrociously pixelated and distorted; this will be fixed in the future, I assume.  The ungated Word-style formatted PDF with correct figures is here, from my ResearchGate page.  The paper itself is pretty big; 90 something manuscript pages; it’ll probably be 30+ pages once formatted.

The paper is pretty broad in scope, and represents quite a bit of work.  As I mentioned above, the rift was basically unknown before we went there, though there was a M ~6.8 normal faulting event in late August 2008 that was studied by John Elliott (paper here) and in more detail by Isabelle Ryder (here).  Both of these papers simply studied the earthquake itself, from remotely-collected geophysical data.  Our study here represents about a month of mapping and sample collection over two campaigns, as well as ~35 new zircon (U-Th)/He cooling ages, 2 zircon U-Pb crystallization ages, and a ton of thermal modeling (~25,000 Pecube runs).  The goal was to have one single, thorough paper that presents all of our observations, data, modeling, interpretations–almost like a treatise on the rift.  It might have been wiser to break it down into several shorter papers, but that’s just not how it went…

In any case, it’s finally out.  Enjoy!

HimaTibetMap now on GitHub

edit 9 June 2013: HimaTibetMap repo on GitHub updated to new address

I maintain HimaTibetMap, an open-source database of active faults in the Indo-Asian collision zone.  While I was in phd school, we hosted the data on KU’s proprietary HawkDrive system, which performed adequately but wasn’t super accessible for other things than downloading.  Furthermore, it was not clear if I would still have access to the site now that I’ve graduated.

So I  have made a HimaTibetMap page on GitHub, the new standard in collaboration websites.  This is where the version I maintain will be.  After discussion with collaborators, I may move the Active Tectonics of the Andes database there as well.

Ideally, this move will make it easier for others to contribute to the database as well.  So if you have anything to contribute, don’t hold back!

Active Tectonics of the Andes (ATA-1.0): A new open-source active fault database, and interpretation

The 1 October 2012 issue of GSA Today (a science and news magazine by the Geological Society of America) features a new article from our research group, primarily written by my friend and colleague Gabriel Veloza.  There are two contributions in this paper: the first is an open-source active fault database called Active Tectonics of the Andes, or ATA-1.0, and the second is an overview of northern Andean tectonics and an interpretation of the overall fault kinematics as resulting from variably-oblique subduction.

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Great BBC documentary on Youtube of mountain building and collapse highlighting Tibet

I was sent a great BBC video entitled ‘Roof of the World’  that does a nice job of outlining many of the modern concepts of mountain building (orogeny) and related collapse (taphrogeny), with emphasis on the Tibetan/Himalayan system and Greece, keeping the tools of the trade central to the story.  There is a lot of gorgeous footage of the dramatic mountain scenery, featuring many of the rock stars of the contemporary academic regime (e.g., P. England, J.-P. Avouac, M. Searle, P. Molnar).  Despite being almost 15 years old, many of the ideas presented here are still driving the science.  The film isn’t as ‘dated’ as some of the commenters would have one believe.  With respect to Tibet and the Himalaya, the only Big Ideas not discussed are the channel flow models of the Himalaya (south-directed, a la Beaumont) and of Tibet (east-directed, a la Clark and Royden), which were published a few years after the movie came out.  There is also not much discussion of the effect of India’s underthrusting of Tibet, either; the situation is presented as a vertically-homogeneous collision, which of course is a problematic approximation.

While I think my favorite part is the scenery, I am very impressed by the ease with which the theories are communicated and the fluidity with which the field and analytical techniques are integrated into the narrative.  The animations definitely help, but a big part of it is simply that many of the modern, cutting-edge concepts in tectonics aren’t actually that complicated.  The treatment of lithosphere as a viscous fluid, the effects of mantle delamination, gravitational collapse, etc., are fairly simple and intuitive concepts.

The genius involved in this kind of work isn’t the mental power and agility necessary to get one’s mind around these ideas, it is the mental power and agility required to look at an enormous pyramid of granite and think of fluid dynamics–actually deriving these concepts from the observation is the hard part.  Well, it’s one of the hard parts.  Figuring out how to quantify and test these concepts (which are hypotheses, of course) against observational data, and to refine, reject and replace them if necessary, is an often harder part.  It’ll be interesting to see what the science looks like in another 15 years–I have some predictions on what will stand, fall, or rise, but these will be tested as well.

Record M8.6 strike-slip earthquake off of Sumatra: The most interesting earthquake in some time

Today’s M8.6 strike-slip earthquake off the Sumatran coast is an incredible event for a number of reasons:  First, it’s (as far as I’m aware) the largest recorded strike-slip earthquake.  Second, it’s an intraplate earthquake–although it is about a hundred kilometers from the Sumatran subduction zone, where the catastrophic 2004 M9.1 earthquake occured), it’s not a plate boundary rupture. However, the stresses resulting from incipient subduction or the effects of the 2004 event likely loaded the fault responsible for this event.  This may also make it the largest reported intraplate earthquake, but I’ll have to check on this. And third, with a centroid depth of 22 km, this is a dominantly mantle event, as the crustal thickness in mature oceanic plates is typically ~7 km.  Since the energy released from an earthquake scales not simply with the along-strike length of the rupture but the total fault area, it’s possible that the great magnitude of this event is a result of a very broad vertical, as well as horizontal, rupture patch.  Additionally, the magnitude scales with the strength of the rock surrounding the fault, and cold (and hence capable of brittle failure) oceanic mantle is made of peridotite and very strong.  Although I have no idea what kind of surface observations are possible for this event, we may find that much of the slip and energy released occurred in the upper mantle.

Well I have to board a plane, so I will cut this off here.  Expect to hear much more about this event in the future, surely from Austin Elliott at The Trembling Earth if no one else.

HimaTibetMap-1.1: An expanded and updated version of the Database of Active Faults from the Indo-Asian Collision Zone- for ArcGIS, GMT, and Google Earth

Edit 3 May 2013: HimaTibetMap is now on GitHub!

I am pleased to announce the updated version of HimaTibetMap-1.1. HimaTibetMap is a database of active faults from the Indo-Asian collision zone, spanning from Iran to Myanmar, and India to Siberia, and contains over 1000 structures.  The area covered is approximately the same size as the contiguous US.  It was originally compiled by Mike Taylor and An Yin based on their field observations, remote sensing analysis, and reviews of the literature, as described in Taylor and Yin (2009). It was since updated slightly by Mike and myself, and released to the public as outlined in our Eos article from May 2010.

Map showing the extent of HimaTibetMap-1.1 made in ArcMap with topography from SRTM.

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