Fay Odak Mekanizmaları
Deprem Odak Mekanizması
Deprem Odak Mekanizması
Doğrultu Atımlı Fay
Ters Fay
Normal Fay
Deprem Odak Mekanizması
Normal Fay
Sol
atımlı
Ters Fay
Sağ
atımlı
Yüzeye
çıkmamış
Ters Fay
Deprem Odak Mekanizması
Deprem Odak Mekanizması
Fay Düzlemi Parametreleri
Kayma
açısı
Fay Düzlemi
Taban
Bloku
Deprem Odak Mekanizması
Tam ters fay
Tam normal fay
Düşey Atım
Sol yönlü Tam
Doğrultu atımlı fay
Dip= ?
Rake=?
Dip= ?
Rake=?
Sağ yönlü Tam
Doğrultu atımlı fay
Deprem Odak Mekanizması
Yandan Görünüm
Üstten Görünüm
Derinlik
Yeryüzeyi
Yardımcı
Düzlem
Fay
Düzlemi
Deprem Odak Mekanizması
Doğrultu Atım
Normal Faylanma
Ters Faylanma
Eğimli Ters Fay
Deprem Odak Mekanizması
Fay Düzlemi
Eğim Atımlı Fay
(Normal)
Doğrultu Atımlı Fay
(Sol yönlü)
Eğim Atımlı Fay
(Ters)
Deprem Odak Mekanizması
Ters Fay veya Bindirme Fay
Normal Fay
Doğrultu Atımlı Fay
Deprem Odak Mekanizması
Tam doğrultu
atımlı fay
Normal Fay
Bileşenli
Doğrultu Atımlı
Fay
Tam Normal
Fay
Ters Fay
Bileşenli
Doğrultu Atımlı
Fay
Tam Ters
Fay
Düşey atım
Deprem Odak Mekanizması
Deprem Odak Mekanizması
Kilometers
1000
100
10
1
5.5
6
6.5
7
Magnitude
7.5
Fay uzunluğu ile Magnitüd arasında ki ilişki
8
Deprem Odak Mekanizması
Seconds
100
10
1
5.5
6
6.5
7
7.5
8
Magnitude
Deprem Süresi ile Magnitüd arasındaki ilişki
Deprem Odak Mekanizması
Okyanus sırtı boyunca oluşan depremlerin tektonizması
Doğrultu Atımlı Fay
(Sol yönlü)
Doğrultu Atımlı Fay
(Sağ yönlü)
Normal
Fay
Normal
Fay
Deprem Odak Mekanizması
Deprem Odak Mekanizması
İlk hareket
YUKARI
İlk hareket
AŞAĞI
İlk hareket
Belirsiz
Deprem Odak Mekanizması
Üç farklı deprem için odak mekanizmaları
ve bazı sismogramlar. Sıkışma bölgeleri
siyah ile taranmıştır.
Doğrultu atımlı fay
Eğim atımlı fay
Ters fay
Normal fay
Düşey atımlı fay
Çeşitli fay geometrileri için deprem odak mekanizmaları.
Sıkışma bölgeleri siyah ile taranmıştır. Tam doğrultu atımlı
mekanizma, ya NE-SW veya NW-SE yönlü düşey fay
içindir. Eğim atımlı mekanizmalar ise N-S yönlü dört fay
içindir.
Deprem Odak Mekanizması
Deprem Odak Mekanizması
Deprem Odak Mekanizması
“Strike” ve “Dalım” açılarının ölçülmesi
Bir fayın “Doğrultusu (Strike Açısı)” kuzey ile yaptığı açıdır.
Dalım açısı (Dip angle) “Strike” açısının sağından ölçülür.
Deprem Odak Mekanizması
“Rake” açısının ölçülmesi
“u” fay düzlemi üzerinde ki
kayma yönü
“Rake”, rölativ olarak “strike” yönüne göre ölçülür.
Kayma (slip) yönü tavan bloğunun
taban bloğu üzerinde ki göreceli
hareketidir.
Tavan
Bloğu
Taban
Bloğu
Deprem Odak Mekanizması
Deprem Odak Mekanizması
Fay Tipi
Tam Doğrultu Atım
Tam Düşey Atımlı Ters Fay
Tam Düşey Atımlı Normal Fay
Sol Yönlü Doğrultu Atımlı Fay
Sol Yönlü Eğim Atımlı Ters Fay
Ters Fay
Sağ Yönlü Eğim Atımlı Ters Fay
Sağ Yönlü Doğrultu Atımlı Fay
Sağ Yönlü Eğim Atımlı Normal Fay
Normal Fay
Sol Yönlü Eğim Atımlı Normal Fay
Deprem Odak Mekanizması
Deprem Odak Mekanizması
Deprem Odak Mekanizması
Örnek 1
1) Use the azimuth (205°) and the plunge (25°) of the dip vector (d) to
plot the trace of the fault plane (f). The fault has a strike of 205° – 90°
= 115°, and a dip of 25° (sameas the plunge of the dip vector).
2) Plot the pole of the fault plane (s’).
3) The reference strike is toward azimuth 115°. Given that the rake of
the slip vector is +70°, it will not plot on a lower-hemisphere stereonet;
however, the antipode of the slip vector (sva) does plot on the
stereonet -- the antipode is 180° from the slip vector. The antipode is
along the trace of the fault, 70° from the primitive circle as illustrated
at left. Project a line from the slip vector antipode (sva) through the
center of the plot
(c) to just beyond the circumference of the stereo plot (i.e., beyond the
primitive
circle). That line, trending 47°, defines the trend of the slip vector. In
the final presentation of the beachball diagram, we are going to leave a
small portion of that line extending from the edge of the diagram to
indicate the direction of hanging-wall slip.
4) Determine the plunge of the slip vector, which is identical in
magnitude to the plunge of the slip vector antipode (sva): the slip
vector plunges ~23° upward, with a trend of 47°.
5) Plot the trace of the auxiliary plane (ap) by using the slip vector antipode (sva) as the
pole to that plane. Note that s’ is on the auxiliary plane.
6) The N axis (n) is located at the intersection of the fault plane and the auxiliary plane.
Determine the trend and plunge of the N axis: it trends 133° and plunges ~8°.
7) Plot the trace of the plane whose pole is the N axis (dashed great
circle).
8) Plot the P axis (p) 45° from s’ and 135° from the slip vector antipode
(sva) along the dashed great circle.
9) Plot the T axis (t) 45° from s’ toward the slip vector antipode (sva)
along the dashed great circle.
10) Determine the trend and plunge of the P axis (p): it trends ~37°
and plunges ~21°.
11) Determine the trend and plunge of the T axis (t): it trends ~243°
and plunges ~78°
Örnek 2
12) Fill the quadrants through which the T axis passes with black, and the
quadrants through which the P axis passes with white. Leave the short line
indicating the direction of hanging-wall slip on the outside of the beachball
diagram.
13) The map is a depiction of the corresponding fault as it exists near the
focus of this earthquake. It is a reverse or reverse-oblique fault with a
comonent of right-lateral slip.
1) Use the azimuth (115°) and the plunge (35°) of the dip
vector (d) to plot the trace of the fault plane (f). The fault has a
strike of 115° – 90° = 25°, and a dip of 35° (same as the
plunge of the dip vector).
2) Plot the pole of the fault plane (s’).
3) Given that the azimuth of the slip vector is 50°, construct a
line from the center of the plot (c) toward azimuth 50°, and
locate the slip vector (sv) where that line intersects the trace of
the fault (f). In the final presentation of the beachball diagram,
we are going to leave a small portion of that line extending out
from the circumference of the diagram to indicate the direction
of hanging wall slip.
4) Determine the plunge of the slip vector (sv): it plunges
~27°.
5) Plot the trace of the auxiliary plane (ap) by using the slip
vector (sv) as the pole to that plane. Note that s’ is located on
the auxiliary plane.
6) The N axis (n) is located at the intersection of the fault plane
and the auxiliary plane. Determine the trend and plunge of the
N axis: it trends 150° and plunges ~30°.
7) Plot the trace of the plane whose pole is
the N axis (dashed great circle).
8) Plot the P axis (p) 45° from s’ toward
the slip vector along the dashed great
circle
(i.e., half way between s’ and sv).
9) Plot the T axis (t) 45° from s’ and 135°
from the slip vector along the dashed great
circle.
10) Determine the trend and plunge of the
P axis (p): it trends ~12° and plunges
~52°.
11) Determine the trend and plunge of the
T axis (t): it trends ~253° and plunges
~23°
12) Fill the quadrants through which the T
axis passes with black, and
the quadrants through which the P axis
passes with white. Leave
the short line indicating the direction of slip
on the outside of the
beachball diagram.
13) The map is a depiction of the
corresponding fault as it exists near
the focus of this earthquake. It is an
oblique fault with components
of normal and left-lateral slip.
Some problems
1. A published focal mechanism solution for a magntude (mb) 6.5 earthquake below
northern Peru on October 28, 1997, lists the azimuth (trend) and plunge of the three
principal axes as follows: T 247, 8; N 337, 0; P 69, 82. What is the strike and dip of the
two nodal planes, one of which is parallel to the fault that generated the earthquake?
What are the orientations (trend and plunge, or rake) of the two possible hanging-wall
slip vectors?
2. In a published datafile listing the fault strike azimuth (right-hand rule), dip angle, and
rake of hanging-wall slip vector, the data for a given earthquake are 135, 60, 120. Make
a FMS beachball diagram (lower-hemisphere stereographic plot) for this earthquake.
3. In a published datafile listing the fault dip direction, dip angle, and rake of hangingwall slip vector, the data for a given earthquake are 216, 65, -100. Make a FMS
beachball diagram (lower-hemisphere stereographic plot) for this earthquake.
4. A field geologist measures the orientation of a fault surface and the direction of
hanging-wall slip indicated by grooves and striations on that surface. The fault’s strikeand-dip in the azimuth method is 35, 63SE, and the rake of the hanging-wall slip vector
is 75° (as rake is defined by seismologists). For no particularly good reason other than a
persistent case of seismologist envy, he wants to represent these data on his map as a
pseudo-focal-mechanism solution beachball (which, by the way, is not a good idea). For
the sake of humoring this poor sod, make a FMS beachball diagram from the field data.
5. You will be provided with a topographic map on which the surface trace of some
faults are indicated. Two earthquake occur in the area. Given the location of the focus of
each earthquake and their respective focal mechanism solutions, project likely fault
planes to the surface to assess if any of the currently-mapped faults are active, or if
there might be a previously unmapped fault in the area.
Deprem Odak Mekanizması
Polarity of first P-wave arrival varies between seismic stations in different
directions, depending on fault geometry.
First motion is compression for stations located such that material near the
fault moves ``toward'' the station, or dilatation, where motion is ``away from''
the station.
When a P wave arrives at a seismometer from below, a vertical component
seismogram records up or down first motion, corresponding to either
compression or dilatation.
Method requires understanding effect of earth structure on seismic waves
Shown are beachball representations of the P-wave radiation pattern for
the three fundamental double-couple fault types: (a): pure strike-slip faulting, (b):
pure dip-slip reverse (thrust) faulting, and (c): pure dip-slip normal faulting. Above
each is a sketch of the fault geometry for that mode of faulting. (The auxiliary
plane is shown as a dashed line.) The compressional quadrants are shaded, and
the sign of the direction of vertical-component rst motion is included for each
quadrant. (Usually these signs are not included.) Such plots are an ecient method
to show trends in focal mechanisms for groups of earthquakes. See, for example,
gures in the paper by Stein & Klosko, 2002. Such plots are also used to represent
non double-couple mechanisms with nodal-plane projections replaced by nodalsurface projections. (After Gubbins, 1990, Figure 6.7.)
Pure dip-slip faults include normal faults and thrust faults. Only three of
the four quadrants are observable in the beachball diagram for pure dip-slip
faults, as shown at right. The center of the beachball plot is white for
normalfaultmechanisms
(a), and the center is black for reverse-fault mechanisms
(b).Reverse-fault FMS diagrams look like my cat’s eyes.
Oblique-slip faults have both strike-slip and dip-slip components. All four
quadrants of a FMS beachball diagram are included for oblique slip earthquakes,
as shown at left. If the center of the beachball plot is in a white quadrant (a), the
fault has a normal component of slip, regardless of which of the two nodal
planes is the fault; if the center is in a black quadrant (b), the fault has a reverse
component of slip.
Deprem Odak Mekanizması
Problem: Given a table of FMS data listing a fault with dip azimuth = 130°,
dip angle = 60°, and rake of hanging-wall slip vector = –125°, reconstruct the
corresponding focal mechanism solution “beachball” diagram and determine
the approximate azimuth and plunge angle of the N, P and T axes. Describe
the type of fault that produced the earthquake.
Based on the focal mechanism solution, construct a map of what the fault
might look like.
Some problems
1. A published focal mechanism solution for a magntude (mb) 6.5 earthquake
below northern Peru on October 28, 1997, lists the azimuth (trend) and plunge
of the three principal axes as follows: T 247, 8; N 337, 0; P 69, 82. What is
the strike and dip of the two nodal planes, one of which is parallel to the fault
that generated the earthquake? What are the orientations (trend and plunge,
or rake) of the two possible hanging-wall slip vectors?
2. In a published datafile listing the fault strike azimuth (right-hand rule), dip
angle, and rake of hanging-wall slip vector, the data for a given earthquake are
135, 60, 120. Make a FMS beachball diagram (lower-hemisphere stereographic
plot) for this earthquake.
3. In a published datafile listing the fault dip direction, dip angle, and rake of
hanging-wall slip vector, the data for a given earthquake are 216, 65, -100.
Make a FMS beachball diagram (lower-hemisphere stereographic plot) for this
earthquake.
4. A field geologist measures the orientation of a fault surface and the direction of
hanging-wall slip indicated by grooves and striations on that surface. The fault’s
strike-and-dip in the azimuth method is 35, 63SE, and the rake of the hanging-wall
slip vector is 75° (as rake is defined by seismologists). For no particularly good
reason other than a persistent case of seismologist envy, he wants to represent
these data on his map as a pseudo-focal-mechanism solution beachball (which, by
the way, is not a good idea). For the sake of humoring this poor sod, make a FMS
beachball diagram from the field data.
5. You will be provided with a topographic map on which the surface trace of some
faults are indicated. Two earthquake occur in the area. Given the location of the
focus of each earthquake and their respective focal mechanism solutions, project
likely fault planes to the surface to assess if any of the currently-mapped faults are
active, or if there might be a previously unmapped fault in the area.
Deprem Odak Mekanizması
Deprem Odak Mekanizması