The places we call home are spread across the globe, and most, though not all, of these are far from the coastal city where our adventure will begin. We assemble gradually over two or three days in the northernmost city in Chile, the lovely port town of Arica. Known as La Ciudad De La Eterna Primavera, or “the City of the Eternal Spring,” the climate here is a rare “mild desert,” an arid region with moderate temperatures year-round. While we are in port the weather is warm and breezy, although the water at the beaches is cold and lifeguards turn away swimmers due to strong currents.

In the center of town is El Morro de Arica, a large hill overlooking the coastline. El Morro oversaw the destruction of Arica in 1868 when an earthquake of magnitude 8.5-9 and the resulting tsunami destroyed the city, and watched again in 1877 as another large earthquake shook the region, this time sparing Arica. Not far west into the Pacific Ocean is the Peru-Chile trench, where the Nazca plate is subducting beneath the South American plate. The trench has a long and prolific history of earthquake activity recorded in the rocks, oral traditions, and written history of Chile. A Mw 8.2 earthquake in April, 2014 in the Pisagua/Iquique region ruptured part of an area that had been quiet for longer than usual, and provided the background for the project we are about to undertake.

From our vantage point atop El Morro we watch as the research vessel R/V Marcus G. Langseth approaches the port of Arica. Soon to be our home for the next seven weeks, she floats slowly into the port after loading most of our equipment in Florida. The science party moves onto the ship on Saturday morning, amid two cruise liners full of tourists visiting the city to eat empanadas and saltenas, and browse the stalls of native crafts and modern souvenirs set up on the weekends. The chief scientist on our cruise is Dr. Anne Tréhu, a professor in the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University in the U.S. The other lead scientists are Dr. Emilio Vera from Universidad de Chile, Santiago and Dr. Michael Riedel from GEOMAR in Germany. I am a post-doctoral research associate at Oregon State. Five graduate students from the U.S., Chile, Germany, and France, three engineers/technicians from Scripps Institute of Oceanography, and one engineer from GEOMAR complete the PICTURES science party. We will be joined on the cruise by the LDEO Chief Science Officer and the technical staff under his direction, protected species observers, and the maritime crew of the R/V Langseth. Together we will travel over 4500 km, recording geophysical data across the source region of the 2014 Pisagua/Iquique earthquake and westward across the trench.

-Kathy Davenport, October, 2016

The map below shows the location of ocean bottom seismometers (OBSs) that we have deployed since leaving port on October 23. These instruments will sit on the seafloor until the end of November, while we generate small seismic sources in a grid above them. The data from this experiment will be used to construct an image of the earth’s crust beneath the seafloor. The instrumentation and the scientific background for this experiment will be discussed in upcoming posts. Fifty of the OBSs are being supplied by the Scripps Institution of Oceanography in La Jolla, California, as part of the U.S. Ocean Bottom Seismic Instrument Program (OBSIP). Nineteen are being supplied by GEOMAR, in Germany. Fourteen of these were recovered from the seafloor after being there for the past year recording aftershocks of the April 1, 2014 Iquique earthquake.