Structuri geotectonice majore in Oceanul Indian si implicatiile lor seismice

[GeoX]

https://eos.org/articles/a-plate-bou...8cCnWJLvpyNgZw

In 2012, two enormous earthquakes occurred near Indonesia. But these massive temblors—magnitudes 8.6 and 8.2—weren’t associated with the region’s notorious Andaman-Sumatra subduction zone. Instead, they struck within the India-Australia-Capricorn plate, which made them unusual because most earthquakes occur at plate boundaries.

On the basis of that slip rate, Coudurier-Curveur and her collaborators estimated the return interval for an earthquake like the magnitude 8.6 one reported in April 2012. Assuming that such an event releases several tens of meters of coseismic slip, a similar earthquake might occur every 20,000 years or so, said Coudurier-Curveur. “Once you release the stress, you need a number of years to build that stress again.”

[real32]

Probabil ca exagereaza putin, dar ce mai conteaza cateva mii de ani la scara geologica! Dorsala Ninety East Ridge reprezinta istoria calatoriei pe care a facut-o India in ultimii (peste) 100 de milioane de ani, inscrisa de hotspotul din Kerguelen in crusta oceanica. S-au facut analize chimice pentru rocile vulcanice din Rajmahal Traps, din estul Indiei (formate undeva spre sfarsitul Cretacicului timpuriu) si s-a constatat ca ele sunt similare cu cele formate din eruptile de lava din Platoul Kerguelen. Deci aproape 120 de milioane de ani, direct spre nord (dar probabil intr-un usor zig-zag ). Marile cutremure din aceasta regiune nu sunt chiar atat de rare. Cateva grade mai spre sud-vest fata de epicentrele megaseismelor din 2012 s-a produs cutremurul din 9 martie 1928, evaluat la o magnitudine Ms 8,1 (Mw 7,7).