What is the relationship between foreshocks, aftershocks, mainshocks and crustal stress? What is the tectonic context of those seismicity patterns with respect to the seismic cycle? To answer such questions, I analyze earthquakes using tools from seismology, statistics, and numerical modeling. My goal is to improve our understanding of earthquake occurrence to enable us to give accurate seismic forecasts to guide hazard assessment and mitigation. To quantify seismic interactions I adopted and developed a set of tools that allow me to study both the overall tectonic framework and individual source properties of earthquakes. From a global investigation, I have found that seismicity patterns on the periphery of large ruptures can provide information about the amount of residual elastic strain before and after the main rupture. Enhanced intraplate aftershock activity (involving diverse focal mechanism geometries) is observed after large shallow rupturing events. I interpret aftershock mechanism diversity as a proxy for extensive regional strain relaxation that intrinsically resets the seismic cycle.