cee 437 lecture 1 - university of...
TRANSCRIPT
CEE 437 Lecture 4
Stereonets
January 15, 2009
Thomas Doe
Bill Dershowitz
Overview
Types of Orientation Data Lines
Planes
Representing them on a Stereonet Polar Plot
Equatorial Plot
Applications Slope stability
Earthquake Analysis
Problem set - out 1/20, due 1/29
Orientations of Objects
Lines: Trend – orientation of horizontal component measured
from north
Plunge – inclination downward from horizontal
Planes Strike and Dip
Quadrant notation
360 Notation
Pole – line normal to plane measured DOWN (Lower Hemisphere)
Dip Vector – Direction of Maximum Dip or Downward Inclination in a Plane
010
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
Schmidt Equal-Area Projection, Lower Hemisphere
Sutu Den Seismic Zones
< 0%
0 -- 1.8%
1.8 -- 3.6%
3.6 -- 5.4%
5.4 -- 7.3%
7.3 -- 9.1%
9.1 -- 10.9%
10.9 -- 12.7%
12.7 -- 14.5%
14.5 -- 16.3%
16.3 -- 18.2%
> 18.2%
# Points: 106
2X 1X2XS
T
8I9I
12I
6X
3X 5X
4X
0 1020
30
40
50
60
70
80
90
100
110
120
130
140
150160
170180190200
210
220
230
240
250
260
270
280
290
300
310
320
330340
350
Schmidt Equal-Area Projection, Lower Hemisphere
All Data Corrected
PoleDip
Vector
Strike
Which is Best?
Quadrant notation cumbersome and hard to use in calculation
Pole, 360 notation, and dip vector compact
Dip vector useful for engineering (problem is biasing of density
in graphics towards vertical – all vertical planes have
same dip vector regardless of strike)
Strike
Dip
Orientation Relationships
Strike and Dip Quadrant – NE or NW, 0-90 degrees, dip direction for NE
Strikes: NW or SE; for NW strikes NE or SW
360 – Strike measured 0-360; Strike is 90 counterclockwise of dip direction (or dip is 90 clockwise of strike)
Dip Vector Direction of maximum dip
Trend – 360 strike + 90
Plunge – dip angle
Pole Normal to plane (lower hemisphere)
Trend – 180 from dip; 90 counterclockwise of strike
Plunge – 90 - dip
Class Exercises
Define line directions on polar plot
Defining a plane
Pole, Dip Vector, great circle
Define plane based on two lines (plane is the
locus of all coplanar lines)
Defining a friction angle as small circle (polar
plot)
Kinematic failure analysis of block and wedges
Hoek, E. and J.
Bray, 1981, Rock
Slope
Engineering
Hoek, E. and J.
Bray, 1981, Rock
Slope
Engineering
Hoek, E. and J.
Bray, 1981, Rock
Slope
Engineering
Hoek, E. and J.
Bray, 1981, Rock
Slope
Engineering
Focal Plane Solutions for
Earthquakes
Stereonet “Beach Ball” Plots
Determine Type of Movement and Fault
Earthquake on a vertical
plane
Edited from Cox and Hart. Plate Tectonics – How it works.
nctr.pmel.noaa.gov/education/ITTI/seismic/Focal_mech_USGS.ppt
Earthquake Planes
USGS
nctr.pmel.noaa.gov/education/ITTI/seismic/Focal_mech_USGS.ppt
Data on the
surface,
interpreted
in 3D
Cox and Hart. Plate Tectonics – How it works.nctr.pmel.noaa.gov/education/ITTI/seismic/Focal_mech_USGS.ppt
With a lot of recordings we can reconstruct
faults with any orientations
Cox and Hart. Plate Tectonics – How it works.
nctr.pmel.noaa.gov/education/ITTI/seismic/Focal_mech_USGS.ppt
Fault types and “Beach Ball”
plots
USGS
nctr.pmel.noaa.gov/education/ITTI/seismic/Focal_mech_USGS.ppt
Example Focal
mechanism diagrams
on mid-ocean ridges
Stein and Wysession, An Introduction to seismology, earthquakes and Earth structurenctr.pmel.noaa.gov/education/ITTI/seismic/Focal_mech_USGS.ppt
Same N-S fault, different
slip direction
Stein and Wysession, An Introduction to seismology, earthquakes and Earth structurenctr.pmel.noaa.gov/education/ITTI/seismic/Focal_mech_USGS.ppt