Page 115 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

97 single, hori- of the sketch: for following refracted distance; line con- “normal” crys- for: Determine horizontal few a mate- t;), solve veloci- layer deep predicted seismic Explain invert- how how normal

Exercises velocity model fronts wave the critical refraction passive and multiple, hori- and strata graph arrival; and t,, (ty, layer each in recorded actual different? of results similar and Discuss a across
Sketch a P-wave the On d) plot and critically f) of length of a plain a vs. distance to direct refraction; basin. several refracted, arrivals. highest-velocity the and comprise arrivals the your models Arctic).

craton. and mantle. P-waves; times P-wave; graph: h) the coastal continental thick. Sketch sedimentary time basement; basement basement depth; ocean an in with model three refracted the and T-intercepts interfaces might profiles refracted with 4.9b they how are and 4.9a) the differences, (Canadian observed that

continental thickness uppermost reflected travel direct on illustrate approximate the “normal” km 5 the of mantle. travel on a crystalline mantle. refraction, relative to Moho depth. recorded layered direct, the direct and overlying the to that refraction and direct Fig. in and (Fig. are How the Bay from

a and Compute e) k) strike, on between approximately velocity uppermost arrivals section; of the resolve resolve was a layers (V,, V2, V3, V4) depths materials of for graph sequence 4-3. and Baffin differs
across approximate of the refracted, graph: and distance; along is top top of the basement refraction, relative to to 4.8 assuming through of the three the on inversion times records similar Exercise the similarities in compute

run a) velocity P-waves. distance Calculate depth. run is P-wave of the P-wave sedimentary the the graph: Fig. lines each of the of arrival travel-time ophiolite in recorded
is crossover is thickness from from necessary necessary in for velocities h3, h3). illustrating Speculate the you
line showing: P-wave critically refracted vs. P-wave. Moho line section showing: and a velocity plot the wave wave the on for crystalline Moho line line profile thicknesses, straight the section. the results shows are and differences. of an profile Explain was
refraction model approximate direct, critically time travel reflected time; j) the resolve refraction Crustal sedimentary model thickness P-wave and times through refracted refracted illustrate for of refraction of refraction refraction and draw on apparent velocity thickness for each knowing (h,, thicknesses a cross-section thicknesses. average 4.9b Fig. hypothetical the How Fig.

hypothetical interface zontal crust; b) for raypaths and direct a on arrivals g) P-wave; intercept i) T-axis to necessary hypothetical margin. tinental oceanic. The interface zontal approximate crust; talline approximate travel Compute wave direct critically critically and Calculate crossover distance crossover distance length length seismic The velocities seismic interfaces. and Ident

EXERCISES A 4-1 c) A 4-2 a) b) ¢) d) e) f) g) h) i) 4-3 a) b) c) d) a) b)

g 500 km South Basin Crust Basin R. B. Smith (1973). From
and Range Province 6.0 Sin 2 72 82 ys km 400 Po "Exotic" km 400 the structure and Cenozoic tectonics ed. by D. C.

Basin —_ SE Mountains, extending into the Cordillera, from Triimpy Union, Washington,

aac Upper Crust Lower Crust ai 400 & -™ 59 _—_ 7 88 ay Swiss Alps ¥ == Collision OY" 2 Z0Ne ZS o lithosphere. Numbers are compressional wave velocity (km/s). for Geological Society of America, Boulder, Colorado. b) Section across the profile below velocity Karner and A. B. Watts, in Journal of Geophysical

Nevada Mountains NS ae 6.4 300 4 “62> 82° — “= 81 : 300 Basin Crusy 300 Fault and Sierra Nevada From Seismic evidence model D. Geophysical

Slerra > 200 0 i}, 6.15 SR at : 200 Malasse lari] nental 200 the San Andreas 1967). and Eaton, Cenozoic Tectonics and Regional Geophysics of the Western 1980). Geological al., ranges, by G. 1983. Redrawn by permission of the American

7 ‘ Co Mant Refraction studies from regions of continental California coast across by permission of The (Rybach et lithosphere at mountain
100 100 European 100 flexure of the ©

‘ from Range Province (Eaton, 1963, 1966; Bateman Pacific coast states, by D. P. Hill, in G. P. Eaton, © 1978. Redrawn western Alps, along the Swiss geotraverse v.88, pp. 10449-10477,
North
0 0 0 Composite section Gravity anomalies and 96
60 30- 60- FIGURE 4.19
b wy a) and of the and Research,