Naomi Barshi's blog

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.

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!

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.

Daily Science Report Explained

Each day, our Staff Scientist/Expedition Project Manager sends out an update to the ship and to our colleagues on shore. The daily report summarizes the scientific findings from the day before. Here's an example of a daily report, explained with photos!

From Mud to Rocks

Agnes just gave us a nice primer on mud. But what happens next to make mud into a rock?
First, we need to answer the question, What’s a rock?

A Successful Story at Site U1480

We finished our first site with success! We're now at our second site, so here's a little summary of what we did at Site U1480. We met our primary science goal at the site: core the entire sedimentary sequence from seafloor down to the oceanic crust that forms the basement that the sediments rest on. That's almost 1.4 km (0.8 mi)!

Weekend Specials

It's the weekend! That means everything proceeds as normal on board, except on-shore colleagues don't read their emails, we don't have video conferences with schools, and we have Very Special Food.

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.

What can we learn from Earth's magnetic field?

While we're casing and preparing to core Hole G at Site U1480, as Agnes wrote about in her recent post, the scientists are mostly working on their reports and discussing their initial interpretations. We have a bit of down time, and we wanted to make use of the great movie lounge downstairs. We watched the geo-fiction movie, The Core.

Today in Geology History: In Memory of Marie Tharp, Pioneering Oceanographer

Think of the first time you saw a map of the world. It probably looked like colorful patches mostly connected to other colorful patches, with a vast scape of blue between the colorful areas. Until the 1940s, that’s how many people imagined the ocean: “a uniform, featureless blue border for the continents.” We commemorate Marie Tharp with a photo of many of the women on the current research cruise of the JR and a brief summary of her work, which includes creating the first seafloor maps of the world's oceans and establishing the global distribution of mid-ocean ridges.

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