While we all heard about the intense Earthquake that hit Mexico September of last year, we are just now really seeing the damage that it did. It has recently been revealed that this 8.2 magnitude earthquake literally cracked a tectonic plate.
Researchers have been going over this for quite some time now and have only recently published their findings in the journal Nature Geoscience. While we don’t know the exact reasons behind why this earthquake was able to do so much damage in the future we hope to better understand things. This earthquake took place in the Pacific Ocean off the west coast of Mexico right along the tectonic border. The whole ordeal itself brought forth a lot of shocking things.
“If you think of it as a huge slab of glass, this rupture made a big, gaping crack,”
“All indications are that it has broken through the entire width of the thing.”
“My real worry over these kinds of events is the tsunami,”
This rupture was able to spread to parts of the slab that were supposed to be compressed and at a depth of about 50 miles, even the bottom edge of the plate was damaged. This is truly fascinating as the rock at that deep of a level should be too squishy to rupture due to the heat down there. There could be a number of explanations for this but researchers have boiled it down to two.
Subduction zones, where two tectonic plates converge, are generally dominated by large thrust earthquakes. Nonetheless, normal faulting from extensional stresses can occur as well. Rare large events of this kind in the instrumental record have typically nucleated in and ruptured the top half of old and cold lithosphere that is in a state of extension driven by flexure from plate bending. Such earthquakes are limited to regions of the subducting slab cooler than 650 °C and can be highly tsunamigenic, producing tsunamis similar in amplitude to those observed during large megathrust events. Here, we show from analyses of regional geophysical observations that normal faulting during the moment magnitude Mw 8.2 Tehuantepec earthquake ruptured the entire Cocos slab beneath the megathrust region. We find that the faulting reactivated a bend-fault fabric and ruptured to a depth well below the predicted brittle-ductile transition for the Cocos slab, including regions where temperature is expected to exceed 1,000 °C. Our findings suggest that young oceanic lithosphere is brittle to greater depths than previously assumed and that rupture is facilitated by wholesale deviatoric tension in the subducted slab, possibly due to fluid infiltration. We conclude that lithosphere can sustain brittle behavior and fail in an earthquake at greater temperatures and ages than previously considered.
What do you think about this? While it might not sound like much it could change a lot of things. Perhaps as time goes on we will come up with a plan to really break down the things to come. For more information on tectonic plates, in general, please check out the video below.
(Image Via: NASA/JPL-Caltech/ESA/Copernicus)