Mühendislik Bilimlerinde Özel
Konular
MUBİ9035 - Mühendislik Bilimleri Bölümüİstanbul Üniversitesi
displacement rate
Almost 1000 stations in Japanese Islands daily measurement of location with accuracy of 1[cm]
1 3 0 Ê 1 4 0 Ê3 0 Ê
4 0 Ê
GPS Earth Observation Network (GEONET)
WAKUYA
OSHIKA
ONAGAWA
RIFU
MIYAGITAIWA
140.9 141 141.1 141.2 141.3 141.4 141.5
38.2
38.3
38.4
38.5
38.67.5 km
Mw=6.0, 2003/07/26 07:13Mw=5.2, 2003/07/26 16:56
Mw=5.3, 2003/07/25 00:13GPS Stations
Aftershocks of M>1.7July 26-September 22
YAMOTO
SHIKAMA
0 2 4 6 8 10 12 14
-15
-10
-5
0
Dep
th [k
m]
Distance [km]
B B'
0 5 10 15 20
-15
-10
-5
0
Dep
th [k
m]
Distance [km]
A A'
Aftershocks of July 26, 2003 (Mw=6.0)
GPS-local stations
Strain rates (Aydan, 2002, 2003)
xu
xx
yv
yy
yu
xv
xy
uv xx yy
x
y
O
Uii
j
k
U j
U k
Vk
V j
Vi
Average Strain Rates computed by using 1st-order
derivative from displacements
Coordinate system and the definition of displacement rates for a triangular element
Displacements
Strain rates
Strain rates
stress rate tensor computed by using Hooke’s law from the computed strain rates for elastic materials.
xy
yy
xx
xy
yy
xx
000202
231
max
Maximum Shear Stress + * Mean Stress Rate
231
m
Disturbing Stress Rate=
Friction of coefficient ( =0.8)
Lame’s Constants ≈ 30 GPa [Fowler, 1990]
Strain rates
md max
2002 2003 2004
0
1
2
0
10
20
30
40
TIME (Julian)DIS
TURB
ING
STR
ESS
RATE
(MPa
)
DISTURBING STRESS RATE
Miy -Wak-Yam Osh-Ona-Yam Osh-Rif -Yam Rif -Miy -Yam Wak-Ona-Yam
MRI
M6.2
M7.0
MRI
=M*1
00/R
=0.8 WAKUYA
OSHIKA
ONAGAWA
RIFU
MIYAGITAIWA
140.9 141 141.1 141.2 141.3 141.4 141.5
38.2
38.3
38.4
38.5
38.67.5 km
Mw=6.0, 2003/07/26 07:13Mw=5.2, 2003/07/26 16:56
Mw=5.3, 2003/07/25 00:13GPS Stations
Aftershocks of M>1.7July 26-September 22
YAMOTO
SHIKAMA
Disturbing stress changes and asperity
D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear DilatD2 0.97 0.81 -0.29 0.28 0.5 -0.39 -0.49 0.49 0.96 0.74 -0.26 0.08D15 0 0.75 -0.38 0.31 0.25 -0.4 -0.39 0.65 0 0.77 -0.28 0.23b 0.03 0.05 -0.1 -0.06 0.39 0.37 -0.1 -0.06 0.06 0.05 -0.1 -0.06Shear 0.52 0.4 0.83 -0.79 0.26 0.39 0.83 -0.79 0.57 0.54 0.83 -0.79Dilat 0.55 0.5 0.9 0.03 0.26 0.12 0.9 0.03 0.86 0.63 0.9 0.03
•Over the full range: A significant positive correlation is observed between seismic clustering (D) and the Gutenberg-Richter b value along the NAFZ strike slip zone.
•Over the 10 -40 km scale: A nearly significant relationship between b and D is observed (r = 0.74, p = 0.06) and suggests that the relationship is primarily associated with deeper or regional scale seismicity since significant correlation is not observed over the 2 to 10 km scale.
•No correlation was observed between seismicity ( b, D2, D15) and GPS strain.
Correlation between seismicity and GPS strain
PositiveCorrelation
NegativeCorrelation
Low-magnitude events(Preshocks)
Large-magnitude events
Afterthoughts on the Izmit Earthquake
Increased b and decreased DC suggest that the rise in the level of low magnitude seismicity and high intensity clustering along the western portion of NAFZ did not completely release stress transferred into this segment of the fault zone (Oncel et al., 1995, Non.Lineer.Geophysics; Oncel and Wilson, 2001, BSSA).
This combination of factors - westward migration along with increased levels of low magnitude
seismicity and higher intensity seismic clustering - are indicators of increased seismic risk in the area.
D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear DilatD2 0.98 -0.29 0.18 0.4 0.48 -0.13 0.18 0.2 0.98 0 0.13 0.67D15 0 -0.38 0.18 0.46 0.12 0.28 0.31 -0.44 0 -0.05 0.15 0.73b 0.36 0.23 0.18 0.21 0.69 0.38 0.18 0.21 1 0.88 0.18 0.21Shear 0.57 0.59 0.57 0.13 0.57 0.34 0.57 0.13 0.68 0.65 0.57 0.13Dilat 0.19 0.13 0.51 0.67 0.54 0.15 0.51 0.67 0.02 0.01 0.51 0.67
•Over the 2-10 km scale: Significant correlation is not observed between seismic clustering and dilatation.
•Over the full range: Significant correlation between b and D is not observed.
•Over the 10 -40 km scale: In this subdivision, seismic clustering (D2 and D15) correlate positively with dilatation (r = 0.67 and 0.73 with p = 0.02 and 0.01 respectively). The correlations suggest that increased rates of extension produce increasingly dispersed seismicity.
Correlation between seismicity and GPS strain
D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear DilatD2 0.76 0.51 -0.25 0.03 0.21 0.44 -0.54 0.38 0.9 0.22 -0.22 -0.41D15 0.08 0.71 -0.68 0.47 0.69 -0.02 0.26 0.46 0.01 0.39 -0.44 -0.1b 0.3 0.12 -0.83 0.73 0.38 0.97 -0.83 0.73 0.68 0.45 -0.83 0.73Shear 0.64 0.14 0.04 -0.6 0.26 0.62 0.04 -0.6 0.68 0.39 0.04 -0.6Dilat 0.96 0.34 0.1 0.21 0.46 0.37 0.1 0.21 0.43 0.84 0.1 0.21
•One would expect seismicity to correlate moreso with dilatation in a subduction zone. However, dilatation along the subduction zone is on average only slightly negative. •Dilatation is positive in the areas to the northeast (17 nstrain/a) and negative (-29 nstrain/a) farther west along the subduction zone. This combination of positive and negative dilatation along the subduction zone is probably responsible for the lack of a more significant correlation between b and dilatation. •The change of dilatation from positive to negative as one goes east to west along the subduction zone suggests a transition in plate interaction from transtensional to transpressive.
•Over the full range: Variations of b value correlate negatively with shear (r = -0.83, p = 0.04) in the zones of this subdivision. The correlation of b to dilatation is weakly positive (r = 0.73, p = 0.1).
Correlation between seismicity and GPS strain
Recommended