Seismicity Seismic Image of Venezuela Basin Seismic waves
Seismicity
Seismic Image of Venezuela Basin
Seismic waves
Seismic wave travel in a homogeneous Earth
Seismic wave travel in which density increases monotonously
Seismic wave travel in a layered Earth
The P-wave shadow zone
The S-wave shadow zone
P and S-wave velocities
The Earth Interior
The Earth Interior
The distribution of land
Hypsographic Curve Extreme elevations are rare l Two common elevations F Ocean basins (abyssal plains) F Continental interiors Why? ? l
The weight of an Object is determined by its mass and the force of gravity F = the force of gravity (weight) g = the gravitational constant (6. 672 x 10 -11 N · m 2 · kg-2) m 1 = the mass of the object m 2 = the mass of the Earth r = the distance between the object and the center of the Earth
Weight varies due to three factors 1. Altitude As altitude increases r increases, so F decreases
Weight varies due to three factors 2. Latitude
Weight varies due to three factors 3. Local variations in rock density
Geographic Survey of India Mid-19 th century Sir George Everest Triangulation systematically disagreed with astronomical near the Himalayas Why?
Archdeacon Pratt’s theory of Isostasy Each block weighs 2 g 0. 5 0. 3 0. 2 density = 0. 1 0. 2 Water density 1. 0 0. 3 0. 5
Astronomer Royal Airy’s theory of Isostasy Wood density 0. 5 8 g 2 g 3 g 5 g 5 g 3 g 2 g Water density 1. 0 Each block weighs 2 g 0. 5 0. 3 0. 2 density = 0. 1 0. 2 Water density 1. 0 0. 3 0. 5
Free-Air correction to 0 ft. Uncorrected gravity profile at 20, 000 ft. Bouguer Corrected profile
Free-air and Bouguer gravity anomaly map of the Alps
Isostasy and Erosion
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