Entry No. 4 | Sept. 14, 2012
The USF team of two has now been in Costa Rica for a week. Over the course of this week, a large international cadre of seismologists, geodesists and volcanologists have assembled in Nicoya Peninsula to study the aftermath of the earthquake.
Dr. Marino Protti of OVSICORI gives an interview for the national press.
Our team has grown from two on the ground (Denis and Jacob from USF) to 12 scientists from the U.S. and Costa Rica. From the states, Georgia Tech, California Polytechnic at Pamona, University of California Santa Cruz and USF are represented. From Costa Rica come three scientists from OVSICORI (The Volcanological and Seismological Observatory of Costa Rica).
The international group has people who study many kinds of earthquakes, volcanoes, and even glaciers, but we are all working very hard on understanding the two moving plates beneath us that caused the big earthquake.
Most of us are working on setting up GPS stations at precise locations to see how the Nicoya Peninsula has moved since two weeks ago.
Some of us are setting out seismometers to find the motion of the ground and detect small earthquakes and aftershocks.
Two scientists are doing precise level surveys on the coastline to see how much the land rose. Locals along the pacific have all told us "the beach is twice as large as it was before the earthquake" and that rocks in the ocean are now visible above the water's surface when "they've never been there before." This suggests that along the shore, the land rose by many tens of centimeters.
Together, we are all working very fast to collect as much data as the crust under the peninsula relaxes after the big jolt a week ago.
-Jacob and Denis
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Entry No. 3 | Sept. 11, 2012
A 7.6 magnitude earthquake, even a deep one, will cause damage to buildings and roads, and we have seen plenty!
On Saturday we got to Nicoya, the eponymous village in the center of Nicoya Peninsula, in northwest Costa Rica. This is very near where the epicenter was originally reported to be. A few glass windows were shattered and there was some rubbish on the side of the road that had been the ceiling of a strip mall that had fallen. Men were replacing the ceiling as we ate lunch.
The damage continued to get worse as we traveled to the south of the peninsula, which is where the epicenter is thought to have been.
In Camas, the cross atop the town center church had broken.
North of Puerto Carillo, a road was buckled in a clean chevron shape and traffic cones had been set out.
Along the main road between Nicoya and the Pacific, large landslides were being cleared from the road. Many of the country roads in the mountains would now be impassable if not for a local rancher handy with a chainsaw.
We stopped and got ice cream in the beach tourist towns Samara (and again in Nosara, because who doesn't need more ice cream so near the equator!) and spoke to the Canadian and American owners. One owner says her mixer fell over: a very big machine! The other, a woman named Robin, saw the dirt road in front of her shop liquify and turn into a wave. New cracks were made in her floor and walls. Her neighbor's windows slid right into his house.
Most remarkable, in our opinion, is the beach. According to official and locals reporting, the beaches at Samara and Nosara grew during the earthquake by many meters! This is because the ground below the beaches was raised and is now higher than before the 7.6.
Everyone is very concerned that the small earthquakes continue. One woman says, "We are getting used to threes and fours around here since last week!"
-Jacob and Denis
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Entry No. 2 | Sept. 10, 2012
Day 1: Delayed at Customs
After arriving in Liberia around noon, we went through customs assuming that letters explaining our work and the name of our contact in Costa Rica would be enough to sail on by. This was not the case. The customs agents decided to send us to a customs broker to import and re-export the equipment. Thankfully, our Costa Rican contact, Dr. Marino Protti, was able to resolve the customs issues such that we didn't have to pay or fill out any paperwork. After a few hours of worry, we were ready to go and set up two of the GPS stations that we brought with us. This, however, was saved for the next day, as the sunset here is roughly 6 p.m. Surprisingly, this part of Costa Rica does not have much light pollution to make the day seem longer. Instead, the nights are as pristine as they can be.
Day 2: Installing the sites
Before installing the GPS stations, we wanted to ask the landowners' permission to do it. This is not as easy as it seems. However, the Costa Ricans are very friendly, and people from the same village know all the landowners. Then, the goal is just to track them down. Most are glad to help out, so we have never been denied entry.
The GPS survey markers are small, metal points anchored firmly into some exposed rock or cement. Finding one in a field of grass is like looking for a needle in a haystack. Even with precisely-measured GPS coordinates, which are accurate to a few millimeters, we are limited by the accuracy of a handheld GPS which we use to look for the points, which is on the order of a few meters. Thankfully, we ran into people at both sites who knew exactly where they were.
To set up a GPS station, we mount a large Frisbee-shaped antenna onto a three-legged mount. In the center is a spike that rests in a small divot at the very center of the survey marker. This has to be precisely level: an antenna off by a degree doubles our error and can show that the land moved in the opposite direction than it actually did! This antenna then sends a data to a receiver at 15 seconds intervals to log the calculated location. Our GPS stations are kept powered by a solar panel and a small lawn mower battery.
Entry No. 1 | Sept. 8, 2012
Large earthquakes occur where tectonic plates flex against each other and then violently slip in opposite directions. Currently, the tectonic plates underneath the Pacific Ocean are subducting or sinking underneath the tectonic plates surrounding the ocean.
On the morning of Wednesday, Sept. 7, the Cocos Plate, one of the Pacific Ocean plates, rapidly jumped a few meters down and northeast 40 km below the Caribbean Plate. This specific portion of the Caribbean Plate is better known as the nation of Costa Rica. The magnitude of this earthquake was a sizable 7.6 on the Richter scale.
A magnitude 7.6 is no small earthquake! To put this size in perspective, a 7.6 earthquake in Costa Rica in 1991 displaced thousands and hundreds of lives were lost. The infamous 2010 Haiti Earthquake was a smaller magnitude 7.0 and killed about 300,000 people. In Haiti, people are still displaced from this single catastrophe. Wednesday's quake in Costa Rica, however, resulted in zero casualties and just 20 injuries.
So why did this bigger earthquake cause less damage? Depth and proximity, mostly. The Haitian quake ruptured 13 km down and only 25 km away from its capital, Port-au-Prince. That's as close as downtown St. Petersburg, Fla., is from the beaches on the west coast of Pinellas County. The 1991 earthquake in Costa Rica was at a similar depth of 10 km. Wednesday's earthquake ruptured an astonishing 40 km below a rural area of Costa Rica, resulting in far less damage. Still, this earthquake was likely the second biggest in Costa Rican history.
We are also lucky for a reason other than the lack of damage from this earthquake. Geologists at USF, along with scientists at other universities, already have a GPS network that surrounds the epicenter of this earthquake. With this, we can get millimeter accuracy of where the land is on the surface of the Earth. After this earthquake, the positions of these GPS stations have changed and we will be able to see that they continue to move for weeks to come. Seismologists and geodesists will use this data to better forecast the earthquake risk in Central America.
We are also lucky because we have a team of geology graduate students leading the data collection. Two students, Denis Voytenko and your humble blogger today, Jacob Richardson, are already in Costa Rica, having landed 50 hours after the quake. We will be blogging our adventurous rapid response throughout the next 10 days as we travel around northwest Costa Rica gathering scientific data to better understand this recent earthquake.