Exploring Patterns of Global & Regional Seismicity

Resource 7 Related Resources Videos Software-Web-Apps Animations Exploring Patterns of Global & Regional Seismicity 1h Novice Resource Files Instructor Guide/Student Worksheets Download All 2MB The Interactive Earthquake Browser shows how earthquakes define plate boundaries In this activity students review their prior knowledge about various types of plate boundaries. Next students use the IRIS Earthquake Browser to investigate well-known examples of some of these boundaries. Students are asked to pay particular attention to the spatial distribution, rate of seismicity, and depth of quakes in each area. Students then point IEB to a new region and are asked to use the “templates” of seismic evidence they have previously constructed for the primary plate boundaries to argue for what is occurring within the mystery region.  Objectives: Students will be able to: Describe the basic properties of crustal rocks Predict how these properties affect interactions at plate boundaries Predict relative ages of crust based on rock properties and boundary interactions Use the IRIS Earthquake Browser to Explore current seismicity of the planet Explore the earthquake patterns at convergent and divergent plate boundaries Identify geomorphological features associated with plate boundaries Apply knowledge to identify a developing plate boundary Identify and describe earthquake pattern in East Africa Use evidence (seismicity and geomorphology) to determine the type of boundary in East Africa    Make predictions about future geomorphology in the region Related Videos Plate Boundaries: Convergent, Divergent, Transform Video lecture covers three basic types of tectonic plate boundaries. Video Novice Related Software-Web-Apps IRIS Earthquake Browser The IRIS Earthquake Browser (IEB) is an interactive tool for exploring millions of seismic event epicenters (normally earthquakes) on a map of the world. Selections of up to 5000 events can also be viewed in 3D and freely rotated with the 3D Viewer companion tool.  Software-Web-App Novice Related Animations Plate Boundary: Convergent margin The subduction zone iswhere two tectonic (lithospheric) plates come together, one subducting (diving) beneath the other. The plates are locked together and periodically overcome the friction causing the leading edge of the overlying plate to surge back, lifting a wall of water producting a tsunami. Animation Novice Plate Boundary: Divergent (Fast-spreading Ridge) New oceanic crust is created at this boundary when basalt magma, formed in the mantle, rises into fractures in the crust and solidifies. Spreading ridges are high elevation because the young oceanic plate at the ridge crest is hot and less dense than the older, colder and more dense plate on the flanks of the ridge.  Animation Novice Subduction Zone: Relative motion with no friction Oblique view of a highly generalized animation of a subduction zone where an oceanic plate is sliding beneath a continental plate with no friction just to show the relative motion between the plates..  Animation Novice Subduction Zone: Simplified model of elastic rebound Oblique view of a highly generalized animation of a subduction zone where an oceanic plate is subducting beneath a continental plate. (See sketch below for parts.) This scenario can happen repeatedly on a 100-500 year cycle. The process which produces a mega-thrust earthquake would generate a tsunami, not depicted here. Animation Novice Subduction Zone: Tsunamis Generated by Megathrust Earthquakes Subduction-zone megathrust earthquakes, the most powerful earthquakes in the world, can produce tsunamis through a variety of structures that are missed by simple models including: fault boundary rupture, deformation of overlying plate, splay faults and landslides. From a hazards viewpoint, it is critical to remember that tsunamis are multiple waves that often arrive on shore for many hours after the initial wave. Animation Novice