Geobulletin alpha

Earliest direct evidence of plate motions 

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Metamorphic evidence of plate tectonic evolution 

Read about tracking ancient paired metamorphic belts using data mining and statistics as a guide to the evolution of modern plate tectonics at Earth-logs Eclogite: the red-brown mineral is garnet, omphacite is green and there is some white quartz.(credit: Kevin … Continue reading →

How does subduction start? 

Robert Stern of the University of Texas at Dallas, USA, and Taras Gerya of ETH, Zurich, have produced a masterly review of how subduction gets started from place to place, and from time to time in geological history (Stern, R.J. … Continue reading →

Recycling of continental crust through time 

Because continental crust is so light – an average density of 2700 kg m-3 compared with the mantles’ value of 3300 – it has been widely believed that continents cannot be subducted en masse. Yet it is conceivable that sial … Continue reading →

Zealandia: a hitherto undiscovered continent? 

Mid-February 2017 saw the announcement in the world’s media of what was made out to be a previously unsuspected, drowned continent. No, not in the Atlantic, but surrounding New Zealand. For geoscientists this was not ‘fake news’, but neither was … Continue reading →

At the Assembly: Friday highlights 

The conference is coming to a close and there’s still an abundance of great sessions to attend! Here’s our guide to getting the most out of the conference on its final day. Boost this information with features from EGU Today, the daily newsletter of the General Assembly – pick up a paper copy at the ACV entrance or download it here. The final day of the conference kicks off with the last Union Session (US3) dedicated to discuss possible avenues of progress towards a commonly applicable [...]

Tectonics & Earthquakes of Himalaya—2015 Nepal EQ 

The tectonics of Guatemala 

To celebrate that I will soon be visiting there, I am digging up various facts. G. is sliced in half by the upper part of the Caribbean Plate.  For some reason the Pacific Plate plunges much more steeply than in Mexico, but produces more volcanoes.  This makes it less likely for big shallow quakes, which is good for me.  Volcanoes are more easily avoided, unless somebody says "Let's look

What is the Indonesian Throughflow? 

On our expeditions page, we wrote out our science objectives for coring along the western coast of Australia. Our focus, as the name suggests, of the expedition is to follow the history of the Indonesian Throughflow (ITF) and the Leeuwin Current to investigate topics like tectonics, climate change, and the development of ocean currents in this region. So what are the ITF and the Leeuwin Current? read

Meeting postponed: NSF workshop on Future Directions in Tectonics 

Some weeks ago we advertised the NSF-sponsored workshop on Future Directions in Tectonics. Yesterday, Kevin Mahan announced that the workshop will be postponed. Read the message he circulated:   WORKSHOP POSTPONED: The NSF-sponsored workshop on Future Directions in Tectonics, to be held in Madison, Wiscons, USA on July 22-24, has been postponed until May 2016. We received a small number of interested responses to the original workshop invitation, due to short leeway time and busy summer [...]

Global sea level rise 

OMG, suddenly the Warmists have attacked Miami. We do know that coastal sea level as defined by tide gauges jumps all over the place. The US east coast has it's own problems, with isostatic rebound, passive continental margin sinking, and groundwater extraction. Tectonics has a big role in sea levels. It's not so huge.  Since sea level was always measured on passive coasts,

Guest blog by Elisa Kagan: New book on the Dead Sea Transform 

A new book on the Dead Sea Transform has been published by Springer: DEAD SEA TRANSFORM FAULT SYSTEM: REVIEWS Together with Prof. Zvi Garfunkel and Prof. Zvi Ben-Avraham, I am a co-editor of this book. The book focuses on various aspects of the fault system, from geophysics, to tectonics, paleolimnology, hydrology, seismicity, and PALEOSEISMICITY. Most relevant to this blog are the papers by Agnon and by Marco & Klinger. Shmulik Marco and Yann Klinger review in a new light

Call for papers: Special Issue on Tectonics of Oblique Plate Boundary Settings 

Our colleague Manuel Díaz-Azpiroz from Seville and his colleeagues will be guest editor of a special issue on “Tectonics of Oblique Plate Boundary Settings”, which is going to be published in Tectonophysics. Everyone who is interested to participate may submit a manuscript. The Special Issue aims on contributions about different aspects of the study of convergent and divergent, ancient and active oblique plate boundary systems, including analytical, numerical and analogue modelling [...]

Topographic and tectonic stress inversions with halfspace: Calculating the topographic stress field 

Background of the topographic stress field calculations The weight of mountains (or other high topography) induces stresses in the earth below the topography. Unlike many other types of stress in the crust, topographic stresses are expected to have very significant spatial variation. Therefore, in regions with high topography, it is important to include topographic stresses into the overall stress budgets of the regions. But because of this spatial variation in topographic stresses, [...]

Topographic and tectonic stress inversions with halfspace: Calculating topographic stresses on a fault 

Topographic and tectonic stress inversions with halfspace: Preparing a coseismic slip model 

Alaska earthquake M6.2 

This was 102 km deep, and the PGV must have been less than 2 cm/s, although the report isn't in yet. Very nice tectonics, but get this. The thing was mostly strike-slip with a bit of subduction thrust.  Very weird, and means absolutely nothing.  Can't wait to see the PGV's and see the soil amplification. Update:  Reference.   Ok, if your office looks like this after such a teeny,

Halfspace: a Python package for elastic halfspace calculations 

Part 1: Introduction I’ve been working the past year and a half on calculating topographic and tectonic stresses. This work has relied heavily on using elastic halfspace approximations, which are quite commonly used in the crustal deformation communities, particularly by geodesists. To this end, I have written a Python module for calculating the topographic stresses in a region, and for doing Bayesian inversions for tectonic stresses that lead to earthquakes. This blog post is an [...]

Topographic and tectonic stress inversions with halfspace: Installation and Configuration 

In order to complete the tutorial, please first clone/download the github repo which comes with the DEM, coseismic slip model, and some auxiliary files, all with the correct pathnames. (Or just download this notebook) Scientific Python installation The first step in using halfspace for topographic stress calculations is to get Python installed w/ the appropriate scientific dependencies. Configuration of Python for scientific computing has historically been a huge pain, but [...]

Topographic and tectonic stress inversions with halfspace: Preparing a DEM