M6.3 earthquake in Taiwan

20:11 | 0 Comments

If you have been listening to the news in the last hours, you probably know already that a M6.3 earthquake has struck offshore Taiwan. As usual, the best information comes from the USGS.

The event happend at 18.05 UTC, and we don't yet have a focal mechanism solution for it. Anyway, in the attached figure you can have an idea of what is going on in there.

Taiwan is located in the boundary between the Phillipine Sea and the Eurasian plates. There is an approximated convergence rate of 80 mm/yr to the SE. What is really especial about this island is the presence of two subduction zones: One, where the South China Sea subducts beneath Eurasia, and another one, where Eurasia subducts beneath the South China Sea, forming both zones approximately a right angle.

You can see a great introduction (including the previous explanation) to the geology of Taiwan in the dedicated website of the California Institute of Technology:

http://www.tectonics.caltech.edu/taiwan/regional.htm


Sources:

- http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/us2009jabu.php
- http://www.tectonics.caltech.edu/taiwan/regional.htm

Comments available again!

21:55 | 1 Comments

In the last days I have been trying to fix the problem we had with the comments, which now they work again!

The problem was fairly simple: although we have our own domain, the blog is enginereed by www.blogger.com, and it seems they don't fit as nicely as we expected.

Probably, if you have been visiting this website in the few days, you have been we have been trying some fancy designs... I promise the final one will have a geological look, just give me a couple of days!!

So... post your comments, they are more than welcome!

Download ASTER GDEM

14:04 | 0 Comments

On Monday 29th of June of 2009, NASA and Japan’s Ministry of Economy, Trade and Industry, released the Global Digital Elevation Model (GDEM) created from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. That has involved the processing of more than a million ASTER scenes, in order to cover Earth’s land surface between 83 degrees North and 83 degrees South.

 

The result is a 30-m resolution digital elevation model available from the following URL: ASTER GDEM . In this website the GDEM can be downloaded selecting by tiles, by polygon, by shapefile and of course, by coordinates.

 

So far the standard DEM was the SRTM data, obtained during a flight of the Space Shuttle in 2000. Its resolution is approximately 90 m (30 for USA), and has proven to be a very valuable resource in structural geology, hydrocarbon exploration, geohazard analyses, etc. GDEM will predictably become a new standard, with a commercial resolution and global availability.

 

 

363788main_pia12090-516.jpg

 

 

Important links:

http://www.gdem.aster.ersdac.or.jp/index.jsp

http://www.nasa.gov/topics/earth/features/20090629.html

 

Problems with the comments

08:59 | 0 Comments

I apologise for the error in the web that doesn’t let you to leave comments in the articles. I will try to fix that in the next days. Apparently it is just a small bug in the template I am using, nothing else! I’ll keep you updated about that.

 

Thanks for reading this humble place :)

 

Jorge

Move and LithoTect for free

10:19 | 2 Comments

Dr. Alan Gibbs, director of Midland Valley Exploration, has announced in the Geo-Tectonics list that their software Move2009 (which includes 2DMove, 3DMove and 4DMove) is now available for free to universities for teaching and research.

 

He recommends contacting MVE through their website or using this email: help@mve.com

 

Move2009, as described by MVE, is “fundamentally different from other geo-modelling and model building software as it incorporates geological time into the modelling process. Other modelling tools simply create good-looking models from the present day interpretations, ours turn the modelling process into a rigorous analytical activity involving geological time, with interoperability support of modelling environments and the ability to easily transfer files between all Move components. Using our products geoscientists can continually challenge and test their assumptions and thereby gain a far deeper understanding into the structural geology they are modelling”.

 

Is that the only geo-modelling software available for building and balancing cross sections and general structural modelling? No. In the same list, Dr. Robert Ratliff, development director of Geo-Logic Systems, reminds that their software LithoTect is also available for free for universities (as it has been for many years). This software combines the power of geological modelling with a very attractive conditions in terms of available platforms and licensing conditions.

 

Well, the choice is in your hands. Perhaps you want to make a comment comparing both suites?

 

 

Earthquakes in Google Earth

19:03 | 0 Comments

A good habit I have acquired during the last months is to take a look to the recent seismic activity of a region before starting to work in there, in order to get a quick idea of what is going on. This habit can be more illustrating that it initially seems.

USGS provides a KMZ file with a very friendly and attractive interface for Google Earth. It loads the major earthquakes in our planet for the last 7 days, classified by time (Last hour, Last day, Last week), and by magnitude (from 1 to 8). If you click on each individual earthquake, you will open a box with its basic information and the url link for opening in your browser the complete information about it.

You can load this file in your Google Earth from the dedicated USGS website for seismology:

http://earthquake.usgs.gov/

It is on the left, "Google Earth KML". Anyway, the direct link to the file is:

http://earthquake.usgs.gov/eqcenter/catalogs/eqs7day-age.kmz

The interface also loads plate boundaries and convergence rates, measured in mm/year. I haven't found the source of the rates, but let's accept that if the data comes from USGS, should be fine. The plate boundaries included in the KMZ file are:

- Subduction zone.
- Oceanic transform fault.
- Oceanic spreading rift.
- Oceanic convergent boundary.
- Continental transform fault.
- Continental rift boundary.
- Continental convergent boundary.

Of course, don't expect a very precise location for the plate boundaries! It is just an indication of the global tectonics of each area, in order to put the earthquakes in a correct geodynamic context.

Personally I find this KML file very useful, not only for the very up-to-the-date information given, but also for the boundaries, the rates... Useful thing when we have to prepare a simple figure in Corel or Freehand for a report.

Again, the links:

http://earthquake.usgs.gov/
http://earthquake.usgs.gov/eqcenter/catalogs/eqs7day-age.kmz

There are more KML's and KMZ's providing similar information, but that will be for another day.

Enjoy!

Graphical templates for Structural Geology

09:28 | 0 Comments

We all need from time to time to print a stereographic projection net, a Kalsbeek counting net or a rose diagram. Courtesy of Holcombe, Coughlin & Associates (http://www.holcombecoughlin.com) today we bring you a document (pdf format) with several graphical templates for structural geology (and mineralogy too!):

http://www.holcombecoughlin.com/downloads/HCA_templates_for_structural_geologists.pdf

The content of the document includes the following diagrams:

Stereographic projection nets (several sizes, 20 cm, 15 cm, 10 cm and 5 cm):

- Lambert equal area projection (Schmidt net).

- Polar equal area projection.

- Equal angle projection (Wulff net).

Rose diagram net

Kaalsbeek counting net

A simple but very useful document, as we can have in a single pdf all the basic diagrams we can need in the field. Now print it and start to plot data!

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