This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
5. Seismology and Plate Tectonics
• Introduction
• Plate kinematics
• Spreading centers
• Subduction zones
• Ocean intraplate earthquakes and tectonics
• Continental earthquakes and tectonics
• Faulting and deformation in the earth
Plate Tectonics Summary (I)
2
Plate Tectonics Summary (II)
Plate Tectonics Summary (III)
3
Global Seismicity
Deep Seismicity
4
Seismicity Cross-section (Wadati-Benioff zone)
Plate kinematics (Euler pole)
5
Relative Plate Motion and Plate Bounday
Angular and Linear Velocity (I)
6
Angular and Linear Velocity (II)
How do we find Euler pole?
• The rates of spreading are found from sea floor magnetic anomalies
The history of reversals of the earth’s magnetic field is knowny g
• The directions of motion are found from the orientations of transform faults and the slip vectors of earthquakes on transforms and at subduction zones
Slip vectors and transform faults lie on small circles about the ppole, the pole must lie on a great circle at right angles to them.
• The rate of plate motion increases with the sine of the distance from the pole
7
Relative Plate Motions w.r.t North America
Relative Plate Motions
8
Pacific-North American Plate Boundary
Global Plate Circuit
9
Recent Plate Boundary Model
Bird, G3, 2003
Rigidity of the plate
(?)+ (?)ikjijk ωωω +=If all plates are completely rigid, above equation should be satisfied
10
Current and Historic Plate Velocities
SLR/VLBI : A few years
NUVEL-1 : Average over three million yearsmillion years
Bend at 43 Ma:
Absolute Plate Motions (I)
Bend at 43 Ma:
Plate direction change?
Mantle wind?
Moving hot spot base?
11
Absolute Plate Motions (II)
Plume?
Ri ht R ll?Richter Roll?
Basin and Range extension?
Propagating Rift?
• Hot spots and intraplate earthquakes (e.g., Hawaii)
• Seismic anisotropy, seismic velocity and absolute plate motion