An introduction to Seismology, Earthquakes, and Earth Structure by Stein and Wysession GEOP 204: Final Exam 20% Mid Term Exam 20% Term Project 15% Class presentation 15% Quiz 10% Homework 10% Class Participation 1 0% Recommended Text and Grading
Lithosphere The lithosphere (derived from Greek, it means “rock sphere”) consists of the crust and the uppermost mantle directly beneath the crust. It is a cold, strong layer and is generally around 50-100 km thick.
Asthenosphere The Asthenosphere ( asthenes is Greek for “weak”, so Asthenosphere is the “weak sphere”) is the region of the mantle directly below the lithosphere. In contrast with the lithosphere, the Asthenosphere is hot and relatively fluid; it will flow over long periods of time. In some sense, the lithosphere “slides” on the Asthenosphere.
CMB is sharp interface between solid mantle and fluid outer core
Core-Mantle Boundary (CMB) P-wave velocity drops from 14 to 8 km/s S-wave velocity drops from 7 to 0 km/s At inner core boundary (ICB), core becomes solid as a results of phase change in iron. Within outer core velocity increases gradually consistent with well mixed fluid
Standard reference model established in 1981 by Dziewonsky and Anderson called PREM (Preliminary reference Earth Model), which is accepted as a Current standard by IASPEI91, AK135. Depth Variation of P- and S-wave
Courtesy of Van Heijst et al. African Super-Plume
Seismic refraction profile recorded in ocean basin, Sheriff and Geldart, 1995 S – Reflections from bottom of water Refraction Interpretation D D - Direct Arrival P P - Lower Crustal Refraction within the crust and from the Moho S
Reflection Interpretation Bowen and White, 1986 A migrated seismic-reflection profile across the Vema Transform Fault on the Mid-Atlantic Ridge at 6°N, approximately midway between the African and South American plates.
Velocity/Density Versus Depth P-Velocity S-Velocity Density