Blog Posts Tagged "earthquakes"

Find Out Which of the World’s Volcanoes are Erupting Today, Today!

One of our main research objectives for drilling the Louisville seamount trail is to try to better understand what is happening in the mantle underneath it. Volcanoes and earthquakes are our most dramatic reminders that the inside of the Earth is not a static ball of rock: there is a fluid mantle that is causing the seemingly solid crust beneath us to move and change.

Geek Blog, entry 1: Some of the science behind my Leg 352 participation....

So, why am I, a seriously land-loving geologist on this ship? Because I have spent my career examining rocks and processes associated with subduction.

What’s an Earthquake?

Earthquakes may bring to mind fear and danger or perhaps confusion and curiosity. Some earthquakes can be very destructive, as we have seen in several recent events. To help mitigate the damage and loss of life, earthquake scientists aim to better understand the physical context of great earthquakes, like the 2004 M 9 Sumatra-Adaman Earthquake. That’s part of the goal of Expedition 362. But first, we need to know what an earthquake is.

The Earthquake that Triggered Expedition 362

In 2004, a magnitude 9.2 earthquake struck the northern Sumatra region and triggered a tsunami that inundated the Indian Ocean coast. The disaster was an important reminder to earth scientists that we must better understand the processes at work in subduction zones so that we can help mitigate future disasters. The earthquake was extremely powerful and surprising to geologists in that it was able to break through the plate boundary to relatively shallow depths (5-7 km) below the seafloor. This poster explains some of the details about the events of 26 December 2004, which spurred the scientists on board Expedition 362 to drill into the seafloor and study the rocks and sediments that host major earthquakes once they reach the subduction plate boundary.

Incoming! Oblique Subduction at the Sunda Subduction Zone

The Indian and Australian Plates plow northeast into the Sumatra subduction zone, part of the larger Sunda subduction zone, at a speed of 45 mm/yr. The angle between the direction these two plates move relative to each other is not always at a right angle (90°) to the subduction zone itself--here it is about 50°. Sliding under the Sunda Plate at an angle is not easy, so several large strike-slip fault systems help to accommodate some of this movement. If you thought learning vectors in high school was pointless—think again. This is a perfect vector component problem!

Not So Fast! Types of earthquakes at the Sumatra Seismogenic Zone

Several different types of earthquakes and fault-slip events happen at the Sunda subduction zone and other subduction zones around the world. Typical earthquakes usually last a few seconds to a few minutes, if they have very large magnitude. But not all fault slip results in typical earthquakes.