Page 223 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

205 Positions and types of flexural bulge. up in zone Extension intermediate to Compression Earthquakes migrating fault as due into the of the as plate basin), 7.23e). beneath fact side various

Interior earthquakes occurring at a subduction Extension at Release of stress built together. c) portion of subducting plate. d) Compression as descending plate or shearing in shallow portion of magma volcanic arc. normal lithosphere occurs earthquakes sinks plate motion compression convergent forearc (Fig. migrates the from other the at

Earth’s 7.23 a) where plates lock or compression in encounters mesosphere. e) overriding plate. f) associated with trench, the of faulting depth the if downward at wedge, converge comes on stations to

of FIGURE zone, b) deep beneath the of part reverse be may plate magma INTERIOR interior recorded
Probes upper Intermediate extension resists there 7.23d) (accretionary plates as earthquakes

as Seaward the on trench the 7.23b). to due mantle arc, (Fig. overriding the as readjustments deep are and
Seismic Waves ee ee eee Compressional Extensional or Compressional zone. subduction the tension to occur due of landward (Fig, 7.23a). Just (Fig. boundary arc volcanic the the if compression the beyond depth mesosphere the the within occur also region forearc the of faulting strike-slip or crustal during 7.23f). EARTH’S OF PROBES Earth’s about have we Earth the

Asthenosphere ease e ee e renee eee eee eee ROEM Oe Strength Gnereasing Mesosphere © Strength High Extensional o . o E arthquakes: along position with varies sometimes earthquakes upward flexes it plate the along friction to beyond and beneath occur or asthenosphere, the great At 7.23c). (Fig. plate encounters descending plate can Earthquakes crust the

CONNOR

Earthquakes at mid-ocean three- Compare with depth) 10 km brittle, newly-formed from shearing stresses Predicted earthquake distributions and focal mechanism Solutions for two different interpretations ridge offset. The two by light illustrated Transcurrent fault. ridge segments are inactive, moving away from each other. Right-lateral, mechanism solutions between and beyond Transform fault. faulting accompanies c

7.21 dimensional views in Fig. 2.22. Along ridge axes, very shallow (< earthquakes are caused by normal faulting during extension of the upper part of the lithosphere. At transform offsets connecting ridge-axis segments, earthquakes result along strike-slip faults. 7.22 FIGURE of a mid-ocean in each case are and dark shading. a) strike-slip focal be observed ridge segments. b) Normal lithosphere at pla
FIGURE ridge system. plates The would the of earthquakes 9.5). In deep and shallow 7.20. Fig beneath dips trench the upper portion The type

magnitudes (My, ~ may inhibit limited to in zone lithospheric plate seaward of the follows 7.23). Fig,

Seismology (Fig. 7.3c). All ever recorded downgoing plate thus are Himalayan-Alpine collision one from just earthquakes zone;

-artnquake depth largest the foci zone, of epicenters zone of (Wadati-Benioff

km the to on earthquake the subduction A plate
/ 700 crust in a zone 7.20).
Knapter as much tion zones, up buoyant 2.18); (Fig. observed At ina wide arc (Fig. contorting

“ever