Dr. Christensen's primary interests are in the field of earthquake seismology and earth structure problems using seismological methods. Research activities include detailed studies of earthquake sources and rupture processes of large earthquakes using a variety of inversion methods and waveform modeling techniques. Recent research has been centered on large earthquakes in Alaska and the Aleutian Islands, including the 1965 Rat Islands, the 1964 Prince William Sound, and the 1986 Andreanof Islands earthquakes. These studies are aimed toward understanding the nature of interplate coupling, asperity distribution, and the dynamics of the rupture process.Research interests include general seismicity studies with emphasis on the spatial and temporal variations of intraplate seismicity and their relationships to subduction zone dynamics. Research which focuses on stress variations over short time periods and possible relationship to larger tectonic stresses are currently underway. Stress variations that are related to the major plate interactions often have far reaching effects, which can be observed in seismicity patterns and stress orientations in the surrounding region. Similarly, stress variations, which can be observed in intraplate settings, may often indicate the stress state of the major boundary.Dr. Christensen is also involved with earth structure studies in various regions of Alaska. These studies use both local and teleseismic data to determine physical properties of the crust and upper mantle.