The two main components necessary for seismic reflection data collection are the air guns and the streamer. The air gun array on the ship contains compressed air (a total of 6600 in³) which is fired off at about 2000 psi. The airguns fire at a set distance interval (either 37.5 and 50 meters for this cruise), which can be adjusted for each line, if needed. The energy from the air guns then travels through the water column, and reflects off the seafloor, or continues through the boundary and reflects off a different layer in the subsurface. These reflections travel back through the layers they penetrated, and through the water column once again. This is where the streamer comes into play. The streamer uses groups of hydrophones in spatial intervals to detect the reflected energy. Hydrophones contain piezoelectric crystals, which detect changes in pressure. The groups of hydrophones detect the signal, then average it for the group, and send it back to the computers on board the ship. There are 1212 channels detecting pressure changes, and the streamer is 15 kilometers (about 9.3 miles) long.

The air gun arrays and streamer can be set to the desired depth (currently 9 and 10 meters, respectively). The air guns are kept afloat by buoys on the surface, and their depth is determined by ropes and metal chains that connect them to the buoys. The streamer is kept afloat with foam inside the tube, and with depth-controlling devices placed periodically on the streamer, called birds. The birds are used to adjust the depth of the streamer while it is in the water, and have wings that are controlled by the onboard computing system and can be directed to move the streamer up and down.  If a big ship is about the steam over the streamer, the birds can be directed to dive.

— Kelly Olsen and Brooklyn Gose

Pictured above are various members of the Scientific Party. All scientific efforts on board are made possible by this wonderful group of people. The technical crew, led by the Chief Science Officer Robert Steinhaus, is in charge of all seismic acquisition hardware and software, including deployment of seismic gear as well as handling the large amounts of data brought in from all instruments. The Chief and Co-Chief scientists are responsible for designing the project, creating a viable project proposal, applying for necessary grant funding, and successfully guiding the project into fruition. Data processors work day in and day out to process data as it is acquired, allowing the science party to view the preliminary images and discuss what we see as we continue with the project. Graduate students are brought on the cruise to learn about the types of data they work on through hands-on experience. Each are assigned a watchstander shift, during which they are in charge of logging navigational information and important mishaps that may occur during acquisition, along with observing and learning about the details of marine seismic acquisition by helping with deployment of instruments and monitoring of instrument software. Finally, Protected Species Observers (PSO’s) accompany the science party on the cruise in order to ensure the experiment does not negatively affect protected species such as pinnipeds, dolphins, sea turtles, and whales. These hardworking people provide the skills necessary to collect high-quality data which will help improve our understanding of earth systems. The collaboration of such minds ensures the efficiency and safety of the cruise, allowing science to take place and learning to continue!

— Compiled by Brooklyn Gose

“CEVICHE “es el nombre del proyecto, el cual representa un esfuerzo de colaboración entre científicos de la universidad de Texas en Austin, Universidad del estado de Oregón y la Universidad de Chile.

En estos momentos nos encontramos a bordo del R/V Marcus Langseth, barco de investigación americano, sustentado por la fundación nacional de ciencias y operado por el observatorio Lamont-Doherty, ambos en Estados Unidos.

Nuestro objetivo es realizar perfiles de la estructura del margen continental, en el segmento costa fuera de Chile central-sur, un recorrido de 1400 km, el cual incluye la región de Illapel (afectada por el terremoto del año 2015), terremoto del Maule (año 2010) y Valdivia ( año 1960). Este proyecto nos dará un mejor entendimiento de las características en los límites de las placas tectónicas, en las zonas de subducción, donde la acumulación de grandes cantidades de energía, y eventos de deslizamiento que se propagan por una gran área sin encontrar barreras, lo que produciría terremoto de mayores magnitudes. Nuestro objetivo general es identificar las características de las estructuras de la tierra, las cuales pueden ser comparadas con observaciones antes realizadas, durante y después de grande terremotos, para así poder tener una mejor imagen y entendimiento de los procesos físicos que llevan a que se produzcan estos terremotos de mayores magnitudes. Este estudio nos mostrará un conocimiento de modelos más preciso y detallado que nos podrá ayudar a anticipar terremotos de grandes magnitudes en las zonas de subducción en los márgenes de Chile, así como en otros lugares.

El día 9 de Enero, antes de dejar el puerto, tuvimos la suerte de ser anfitriones de distinguidos visitantes, en los que se incluía la presidenta de la república de Chile, Michelle Bachelet, el presidente de la fundación chilena de Ciencia y el embajador norteamericano en Chile. Tanto la tripulación como los científicos y los líderes técnicos del proyecto Ceviche discutieron los objetivos del crucero destacando los instrumentos que se utilizarían en este proyecto.

Para más información, se pueden dirigir a el siguiente enlace http://impresa.lasegunda.com/2017/01/13/V/fullpage#slider-8.

Luego de recargar combustibles a las afueras de la costa de Valparaíso, comenzamos nuestra travesía en la tarde del 11 de enero.

Los invitamos a volver a este blog, el cual se estará actualizando constantemente con más información de lo que vayamos aprendiendo.

This cruise represents a collaborative effort between scientists from the University of Texas at Austin, Oregon State University and the Universidad de Chile. We are currently on board the R/V Marcus Langseth, a US research ship supported by the National Science Foundation and the operated by the Lamont-Doherty Earth Observatory.

Our goal is to image the structure of the continental margin along a 1400-km long segment offshore south-central Chile that includes the source region of the 2015 Illapel , 2010 Maule and 1960 Valdivia earthquakes to better understand the characteristics of the plate boundary that allow subduction zone slip events to grow into giant subduction zone events. All earthquakes begin small; a great earthquake occurs when the plate boundary remains locked long enough to accumulate enough strain in the adjacent plates to lead to a large amount of slip and when that slip can propagate over a large area without encountering barriers. Our overarching objective is to identify features of Earth structure that can be compared to other geophysical observations made before, during and after large earthquakes in order to better understand the physical processes that lead up to a great earthquake. This knowledge should result in more accurate and detailed models for interpreting ongoing observations in an effort to better anticipate great earthquakes in the Chile subduction zone and elsewhere.

On January 9, prior to leaving port, we hosted tours of the ship for distinguished visitors, including President Michelle Bachelet of Chile, the President of the Chilean Science Foundation and the US Ambassador to Chile. The ship’s crew and the scientific and technical leaders of the CEVICHE science party discussed the objectives of the cruise as well as highlighting the tools to be used for this project. For a discussion of cruise objectives in Spanish, see http://impresa.lasegunda.com/2017/01/13/V/fullpage#slider-8. After refueling while at anchor off Valparaiso, we got underway on the evening of January 11.

We invite you to return to this blog as we add posts about life at sea, who we are, what we are learning.