In conjunction with Caltech and the Geophysical Institute of Peru, we installed our network of 49 seismic sites across steep and shallow subduction regions in Peru. Flat slab subduction is thought to have formed much of the major geology of the western United States some 100 million years ago. By examining such processes presently active in Central and South America we can piece together the history. The data from the Peruvian sites is delivered to UCLA every night and we have collected almost 1 year so far. In the GeoNet experiment, the science objective is to use a rapidly installable wirelessly linked seismic network to make near-real time unaliased observations in aftershock or volcanic zones. The immediate technical objective is to collaborate with Reftek to construct a new generation digital acquisition system (DAS) based on the CENS-developed LEAP (low-power energy aware processing) system and a newly developed low-power A/D converter from Texas Instruments. We also look into the possibility of using the cell phones for seismic data collection and research. Phones are increasingly being equipped with not only accelerometers, but also cameras, Global Positioning System (GPS) receivers and Internet connectivity. This makes them very attractive for use in data mining. We have tested a number of small USB accelerometers and a cell phone on a shake table and the results are encouraging.
We have examined seismic data and wireless network characteristics from 100 broadband stations installed from Acapulco to Tampico in Mexico over a period of 1.5 years (2005-2007). The instruments were part of the MASE (Middle America Subduction Experiment) which has the objective to build a geodynamical model of the subduction process beneath the Middle America Trench. The stations had a 5-6 km spacing and were connected wirelessly with each other providing a unique data set. It allows examination of various aspects in tomography, shear wave splitting, wave travel times as well as extensive analysis of the wireless network used for data delivery. Tomographic and SKS splitting studies in this area show the presence of a 50-80 km thick flat slab under the western part of the array, and a steeply dipping slab beneath its center to a depth of ~550km and ~375 km inland.
The research in wireless area displays no correlation between SNR and throughput and a rough correlation between the throughput and the distance for the majority of the links. Various network tuning techniques were applied to further investigate the properties of the communication hardware and data transmission. A new disruption tolerant shell (DTS) was tested that provides duplex communication with the network and handles breaks in the RF communication by temporarily storing data and transmitting when a conection has been restored.
This work describes preliminary results from a 50 station broadband seismic network recently installed from the coast to the high Andes in Peru. UCLA's Center for Embedded Network Sensing (CENS) and Caltech's Tectonic Observatory are collaborating with the IRD (French L'Institut de Recherche pour le Developpement) and the Institute of Geophysics, in Lima Peru in a broadband seismic experiment that will study the transition from steep to shallow slab subduction. The currently installed line has stations located above the steep subduction zone at a spacing of about 6 km. In 2009 we plan to install a line of 50 stations north from this line along the crest of the Andes, crossing the transition from steep to shallow subduction. A further line from the end of that line back to the coast, completing a U shaped array, is in the planning phase. The network is wirelessly linked using multi-hop network software designed by computer scientists in CENS in which data is transmitted from station to station, and collected at Internet drops, from where it is transmitted over the Internet to CENS each night. The instrument installation in Peru is almost finished and we have been receiving data daily from 47 stations (out of total 49) since Jan 2009. Two remain without any network connectivity. The software system provides dynamic link quality based routing, reliable data delivery, and a disruption tolerant shell interface for managing the system from UCLA without the need to travel to Peru. The near real-time data delivery also allows immediate detection of any problems at the sites. We are building a seismic data and GPS quality control toolset that would greatly minimize the station's downtime by alerting the users of any possible problems.
Data, statistical models and inferential procedures permeate CENS deployments, from the four founding scientific application areas to the more recent urban sensing campaigns. This cross-center research breaks down into three classes of research: 1) General statistical models for embedded sensing, with specific applications to data quality and continuous sampling, 2) Significant CENS-designed and supported databases and repositories, and 3) Studies into the data lifecycle for embedded sensing systems.
The Summer@CENS Research Scholars Program continues to be one of the key Education initiatives at CENS. The program is the core of our educational pipeline and is an excellent example of aligned Center research and education activities. The Summer@CENS Research Scholars Program serves as an umbrella for our undergraduate and high school summer research opportunities. It brings together talented undergraduates from around the country and local high school students to engage in Center research for 8-10 weeks over the summer. This poster highlights the structure of the program from planning to implementation as well as some of the outcomes resulting from the program. Also highlighted is the CENS Intel Scholars Program which allows us to extend the summer experience through the academic year for undergraduates at UCLA. This year, the CENS High School Scholars program has also been extended through the academic year to support continuation high school students in Central High School in the Mar Vista Projects.