The large faults that separate oceanic plates from continental plates in subduction zones generate the largest earthquakes and giant tsunami. Examples include earthquakes with magnitude 9.0 and larger in Chile in 1960, Alaska in 1964, Indonesia in 2004, and Japan in 2011. These giant earthquakes have significant economic and social impact causing loss of life and livelihoods, damage to buildings and infrastructure, disruption of business, and changes in communities that can take years for recovery. Modern instrumentation provides scientists the opportunity to study these faults and the earthquakes they generate in new ways. In April 2016, the Pedernales Earthquake ruptured the subduction zone along the coast of Ecuador in a large Mw 7.8 earthquake. An international rapid response effort deployed a seismic array to record aftershocks following this large earthquake that expanded long term observations of the national seismic and geodetic network in Ecuador. Analysis of these data provide an opportunity to link variations in structure and seismic properties along the subduction zone to the distribution of slip behaviors observed before, during, and after the earthquake. The broader impacts of this research have the potential to benefit society through improved hazard assessment and mitigation strategies for subduction zone earthquakes. A spectrum of fault slip behaviors (earthquakes, non-volcanic tremor, slow slip events, low-frequency earthquakes and very low-frequency earthquakes has been observed in a number of subduction zones globally. While a general framework has developed characterizing the variation in slip behaviors in the dip direction along the plate interface, a direct link between seismic properties and slip behavior and the relationship between slow-slip events and megathrust earthquakes has yet to be established. In April 2016, the Pedernales Earthquake ruptured an approximately 130 km long, 100 km wide segment of the subduction zone along the coast of Ecuador in a large Mw 7.8 megathrust event. Immediately after the earthquake a coordinated international rapid response effort deployed a seismic array (on land and offshore using ocean bottom seismometers, OBS) above the rupture zone and adjacent fault segments where large earthquakes occur on decadal time scales and slow slip events have been observed. The dense on land array combined with offshore OBS instruments provides an exceptional dataset to study the earthquake and aftershock sequence. The seismic array is complemented by rapid response geodetic efforts and long term observations from permanent national seismic and geodetic networks in Ecuador. The researchers will use subduction of the Nazca Plate beneath Ecuador and the Pedernales Earthquake and aftershock sequence to link along strike variations in structure and seismic properties to the distribution of slip behaviors observed (pre-, co- and post-seismic) to determine the relationship between slow slip and megathrust rupture. The integrated analyses from a variety of broadband seismic techniques will be used to examine the persistence of asperities for large to great earthquakes over multiple seismic cycles, the role of asperities in promoting or inhibiting rupture propagation, and the relationship between locked and creeping parts of the subduction interface. Broader impacts of this research will contribute to improved risk assessment from subduction zone earthquakes. In addition we are partnering with Build Change, a non-profit NGO, to develop materials to educate local communities on earthquake hazards and construction techniques to improve resiliency. This project supports academic research infrastructure in seismology and computation, and professional development and training for early career scientists. Results from this research will be integrated into STEM education at both the graduate and undergraduate level. This project is cofunded by the Office of International Science and Engineering.