The Middle America Subduction Experiment (MASE) is a collaborative project between California Institute of Technology, Universidad Nacional Autonoma de Mexico (UNAM) and UCLA CENS. The project is instrumenting a 500-km transect from Acapulco to Mexico City to Tampico by installing 100 broadband seismometers located every 5 to 20 km. UCLA has installed almost 50 seismometers covering nearly one-half of the line and is using telemetry technology designed by CENS. The entire line will be operating for at least one full year. The seismic data collected by UCLA seismometers is delivered to a RAID array at UCLA in near real time for archiving, processing, and analysis. We are mapping the structure of the Cocos plate subduction zone underneath the Pacific plate along the transect and examine slow earthquakes, volcanic earthquakes and propagation of seismic waves in the heavily populated Mexico City region.