Page 218 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

Focal mechanism solution,
illustrating strike and dip of earthquake
1,2,
Features
extension.
a
locked
slide
segments
boundaries
centers),
following
(Figs. 2.13, 2.14).
201
of
and auxiliary fault planes,
view
plates
text.
are
Tectonics
(spreading
zone
transform
map
during
zones, plates
and 3 discussed in
of
as
shearing
types
narrow
7.18
the
hot
Plate
downdropped
FIGURE
in
two
axes
region
active
and
illustrated
the
to
fracture
7.21). The
ridge
due
with
the
Earthquakes
the
Plane
of Fault or
offsets
keeps
At
coincide
inactive
of
are
along
is
motions.
35°
(Fig,
Angle
2 s
blocks
Auxiliary
solutions
asthenosphere
transform
=
occur
commonly
faults
axes, on
there.
Dip
crustal
fault
Portion
earthquakes
transform
mechanism
occur
at
ridge
of
90°
occur
as
7,
earthquakes
basis
the shallow
earthquakes
Inside
occur
the
=
earthquakes
adjoining
the
Beyond
focal
earthquakes
Most
on
to about 7.5), because
ridges,
distinguished
of
no
ridges.
another.
and
utility
together; almost
fault
mid-ocean
axes
fault
the
Strike-slip
The
ridge
one
between
normal
be
past
Plane
or
can
the
At
of Fault
Auxiliary
Dip
aye
meee
to ridge 1960's the to Prior 7.22). (Fig. segments ridge mid-ocean two connecting fault ¢ranscur- along another one from apart moved have to interpreted were segments follows: as be would seismicity concept, this to According 7.22a). (Fig. faults rent zones fracture the on and ridges the between occur earthquakes strike-slip 1)
and dilatation. patterns depend on mechanism focal is equivalent focus. Fault compression, = C inside
focus, and quadrants of compression and dilatation. The or of dilatation. c) The fault, this projection dip-slip earthquake Normal the in (black) (b). fault normal for a
Earth's Surtace of compression flying over the bird b) ‘, has compression (a) is observed
Seismology Earth's Surface fault, earthquake reveal patterns from quadrants of compression lower focal sphere projection. For a by a pattern viewed Cross sections of lower focal sphere and focal mechanism solutions for dip-slip faults. fauft reverse for a (white); the opposite pattern
Earthquake “ % Waves Leave Focus ‘ , Waves Leave Focus N *., as Compression Cross section of reverse the surface focus of the is commonly a radiation dilatation. = Fault focal mechanism solution
Chapter 7 Waves Leave Focus Ss as Compression,“ ., al i, %, “Hae! . a / a) motions observed at region the left fault compression; white Reverse regions of dilatation
’ ‘ : Waves Leave Focus 43 Dilatation 7.16 tays for a the compression/dilatation
200 FIGURE First b) whether solution = Black @) 77 dilatation. The by surrounded
' — o-
j
j