Eryn Klosko

Consistency of geologic and geodetic displacements during Andean orogenesis

Displacement and convergence rates inferred from GPS and marine magnetic data suggest that this trend may be continuing at present. Hence an increasing fraction of convergence is being absorbed by mountain building. This change may reflect increased plate coupling due to decreased sediment supply, younger subducting lithosphere, or increased normal stress at the interface from the effects of uplift. INDEX TERMS: 8102 Tectonophysics: Continental contract orogenic belts; 8157 Evolution of the Earth: Plate motions—past (3040); 8158 Evolution of the Earth: Plate motions—present and recent (3040); 8099 Structural Geology: General or miscellaneous

7 Earthquake mechanisms and plate tectonics

Earthquake seismology has played a major role in the development of understanding of global plate tectonics and in turn making plate tectonics the conceptual framework used to consider most large-scale processes in the solid Earth. Because earthquakes occur primarily at the boundaries between lithospheric plates, their distribution is used to map plate boundaries and their focal mechanisms provide information about the motion at individual boundaries. Plates are formed at ridges and subducted at trenches. At transform faults, plate motion is parallel to the boundaries. The basic principle of plate kinematics states that the relative motion between any two plates can be described as a rotation on a sphere about an “Euler pole.” The direction of relative motion at any point on a plate boundary is a small circle, a parallel of latitude about the “Euler pole.” Earthquake mechanisms from the mid-ocean ridge system generally reflect the spreading process. These mechanisms are also used to study the internal deformation of major plates. Although idealized plates are purely rigid, the existence of intraplate earthquakes reflect the important but poorly understood tectonic process of intraplate deformation.

Technology in introductory geophysics: the high - low mix

Abstract Geophysical concepts are challenging to teach at introductory levels because students need to understand both the underlying physics and its geological application. To address this, we are upgrading an introductory course with a mix of ‘high’ and ‘low’ educational technology. The primary focus is ‘low’ technology, using class demonstrations and experiments to demonstrate underlying physical principles and their geological applications. We integrate these into the course, together with the ‘high’ technology of computer simulations and the vast resources of the World-Wide Web, using a course webpage (http://www.earth.nwu.edu/people/seth/B02). The ‘high’/‘low’ mix provides students with different representations of the same concept. We hope that by using both methods, we help students to better visualize concepts from class. Simulations and demonstrations also serve as a break from a steady diet of equations and make the class more fun for instructors and teaching assistants to teach.