ESS 119: Euler Poles, Relative Rotation Rates, and Relative Velocities DATA: DeM

ID: 77569 • Letter: E

Question

ESS 119: Euler Poles, Relative Rotation Rates, and Relative Velocities

DATA: DeMets et al. [1990] produced the following global model for present plate rotation rates, called NUVEL-1. Each Euler vector is relative to a Pacific-plate reference frame. Rotations which are counterclockwise (when looking at the Earth from space) are considered positive. (Notice that when we take the Pacific plate as the reference frame, all rates become rather large and all Euler poles lie in the Northern hemisphere!)

Moving plate, x

Latitude of pole

Longitude of pole

Rotation rate,

(w.r.t. Pacific)

°N

°E

{radians}/s

Africa

59.160

-73.174

5.362Ã—10-16

Antarctica

64.315

-83.984

5.029Ã—10-16

Arabia

59.658

-33.193

6.424Ã—10-16

Australia

60.080

1.742

6.214Ã—10-16

Caribbean

54.195

-80.802

4.720Ã—10-16

Cocos

36.823

-108.629

11.553Ã—10-16

Eurasia

61.066

-85.819

4.969Ã—10-16

India

60.494

-30.403

6.382Ã—10-16

Nazca

55.578

-90.096

7.866Ã—10-16

North America

48.709

-78.167

4.330Ã—10-16

South America

54.999

-85.752

3.682Ã—10-16

Compute the velocity of the Pacific plate with respect to the North America plate at Palmdale, CA (34.5 °N, â€œ118 °Wâ€ = -118 °E). Do this by hand, and turn in all the steps of the computation. Your final answer should be a velocity-magnitude and an azimuth. Compare the results to a geologic map (measuring the azimuth of the San Andreas fault with a protractor), and discuss what type of plate boundary is expected at Palmdale today.