//
you're reading...

Geology

SURFO Special: Surveying hazardous faults during Eastern Haiti’s 270-year earthquake hiatus

 

Each summer, the University of Rhode Island Graduate School of Oceanography (GSO) hosts undergraduate students from all over the country to participate in oceanographic research. These Summer Undergraduate Research Fellows (SURFOs) have not only been working with GSO scientists, but they have spent part of their time learning how to communicate this science to the public. Read on to find out what they have been up to, and why they everyone should be as excited as they are about their work.

This post was written by Kamal James. Kamal was a summer intern (SURFO) at the University of Rhode Island Graduate School of Oceanography working with Dr. Marie Helene-Cormier to analyze seismic reflection (aka CHIRP) data from a fault system involved in the 2010 earthquake in Haiti. He is a graduating senior in Earth Science from Lehman College in the Bronx, New York.

— — — — — — —

“What does a lake have to do with oceanography?”

Individuals wander among debris caused by the devastating Mw 7.0 earthquake of January 12th, 2010. (image credit: Britannica)

Haiti – a country positioned at the Caribbean and North American plate boundary – is no stranger to seismic activity. In January 2010, the poorest country in the Western Hemisphere experienced the fifth most catastrophic earthquake in the world. The magnitude 7.0 earthquake that shook Haiti in 2010 resulted in around 250,000 deaths and 1.3 million people displaced in and around the capital of Port-au-Prince.

Unlike the highly tectonic regions of California and Japan, Haiti’s infrastructure is not seismically retrofitted to withstand earthquakes such as these. Unfortunately, the socioeconomic conditions in the country prior to the earthquake and lack of sufficient building codes contributed to the magnitude of the resulting humanitarian crisis. Considering the percentage of Haiti’s population that was killed or severely impacted, the quake could be considered the most destructive event any country has experienced.

In a region with a long recorded history of quakes – the earliest documented in 1562 – it is only a matter of time until the island of Hispaniola is due for another potential disaster. GPS stations positioned along the Enriquillo fault zone document a combination of compressive (smushing) and strike-slip (scraping) motion across the region at a rate of 1.1 centimeters per year (cm/yr).

Using GPS to track seismic movement

The red dot represents the epicenter of the January 2010 earthquake. In yellow, the Enriquillo fault system trends EW and intersects Lake Azuei. (image credit: Project Lake Azuei)

Thanks to this GPS data, I’ve been able to validate some of my findings this summer. While it is difficult to forecast earthquakes, it is possible to predict the risk in the event that one occurs. Using some math, I was able to calculate the extent of movement for the imminent and overdue earthquake expected in Eastern Haiti.

1.1cm/yr doesn’t seem like much until you account for the lack of a quake in the region for nearly three centuries. The last earthquake to rupture along this fault zone was 270 years ago in 1751 – and since I know that converging motion is about 1.1cm/yr, I simply multiplied the number of years by the relative motion (270 years x 1.1cm/yr = ~ 3 meters). This is called a slip-deficit – or the amount of motion that has yet to be released – which is about 10 feet! Forecasting this earthquake is no easy feat, but with the use of unlikely survey methods and a lake, we can help identify and mitigate associated risks.

Now, I know what you’re thinking; what does a lake have to do with oceanography? The answer may lie beneath the lake bed – but not without the help of oceanographic survey methods.

“Ok, so why Lake Azuei?”

Satellite image of Lake Azuei. Haiti is located on the lower left and the Dominican Republic is located in the upper right of the image. (image credit: Google Earth)

Lake Azuei, known locally as “Etang Saumatre,” is the largest lake in Haiti, and conveniently nestled within this seismically complex region. Located about 60 kilometers (km) east of the 2010 earthquake epicenter and about 30 km east of the densely-populated capital Port-au-Prince, its proximity to the Enriquillo fault zone may reveal crucial morphological features beneath.

During a marine seismic survey, a boat tows a device that releases sound waves (or CHIRPS) to the lake and beneath the lake bed. Sound waves are reflected back to hydrophones usually attached to the stern of the boat. This data is processed using interpretation software. (image credit: Project Lake Azuei)

Studies since the 2010 earthquake reveal that there’s deformation around this fault zone. Unlike on land, tectonic deformation is well-recorded in lake sediments where deposition is more continuous. Acquiring subsurface seismic profiles on land is logistically difficult since it’s hard to imagine asking someone to use their backyard to deploy clunky machinery. Not to mention, terrestrial features like folds, faults, and hills are subject to erosion, effectively removing pieces of the puzzle we’re trying to solve.

Use of lakes offer advantages over oceans as well. Their ease of access and well defined basins facilitate great stratigraphic correlations. Compared to the ocean, lakes are relatively shallow, which allows surveys to be carried out using lightweight geophysical equipment deployed from small boats. In short, investigations within lakes can be cheaper and less laborious.

Oceanographic Survey Techniques

Here, Kamal is using OpendTect in order to interpret the collected CHIRP data from the 2013 and 2017 excursions.

The structure and morphology of features below Lake Azuei are poorly understood. To improve our understanding of plate motion and deformation within the Enriquillo fault zone, scientists embarked on a seismic survey in 2017 (a method typically used in marine investigations). Using a boat and CHIRP sonar, a high frequency sound wave was transmitted below to the lakebed and reflected back to hydrophones towed along the boat. Not only does this device profile the lakebed, but also the geologic structures beneath the lake bed. This information was visualized in real-time during the survey, but remained to be analyzed by yours truly. One of my tasks this summer was to process, analyze, and interpret 400 km of CHIRP data from the 2017 field excursions, and an earlier excursion from 2013.

“Then what?”

After analyzing and interpreting the CHIRP data files, these morphological features will be mapped using software called GMT (Generic Mapping Tools). I’ll be generating some useful maps throughout the fall to be presented at AGU 19’. Stay tuned and check out www.projectlakeazuei.org!

 

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 3 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 4 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 5 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 7 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 9 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 9 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 10 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 10 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 11 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 11 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 12 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 12 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 1 year ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com