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Failure Build-up of stress (strain energy)
Dicult to predict time and place Breaks at weakest point Hear precursors Sound of breaking same as seismic wav
Breaking of !opstick
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Sources of "sunami
Sudden submarine topographic change
Crustal deformation by earthquake.
Submarine volcanic eruption.
Landslide near coastline or
submarine landslide.
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"sunami by #olcanic $ruption
Ref. http://www.geology.sdsu.edu/howvolcanoeswork/!rakatau.htmlMore than 36,000 peoplewere killed.
"ruption of !rakatau in #ug.
$%%&.
!rakatau
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"sunami by %andslide
'he landslide was triggered by
an earthquake on (ay )$* $+,).
(ore than $-* people were
killed mainly by tsunami.
Landslide
'sunami
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"sunami by $art!&uake
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$% 66
$. eneration of 'sunami $. eneration of 'sunami
). 'sunami rade 0 ). 'sunami rade
&. "1pected arrival time &. "1pected arrival time 2. Expected tsunami height
Empirical method a3 4istance to epicenter
b3 (agnitude of earthquake
Quantitative methodSimulation of tsunami
$% 55
5. 6ntroduction of Simulation 'echnique7since $,,,3
average issuance time
& to - min
Occurrence
of
Earthquake
Detectionof
Seismic
Wave
Determinationof
Source
Parameters
Evaluation
ofTsunami
Issuance
of
TsunamiWarning
Mp
Dedicated telephone netor!
"trong motion
seismograph
#utomatic $rocessing "%stem
"hort&period
seismograph
Quantitative Tsunami Forecast
7/23/2019 Session I.4 Yamamoto
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'!at is t!e $art!&uake Source $lastic ebound
Fault Slip Double-couple Force
Seismic *oment "ensor
*odels of $art!&uake Faults
$art!&uake Si+e *agnitudes Seismic *oment $nergy
"!eoretical Seismology , Sources
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'!at is t!e cause of $art!&uakes
.ssociated wit! faults (source or cause)
.ssociated wit! magma
(*ost) $art!&uakes arefault movements
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"ypes of faults
"!rust (everse) fault
/ormalfault
Strike-slip fault
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Strike-Slip Faults
%eft-lateral ig!t-lateral
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,012 3mperial #alley4 alifornia (*s 56,)
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San Francisco $art!&uake.pril ,74 ,028
*w 565-560152 km rupture ofSan .ndreas fault
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Japan Meteorological Agency 2005/3/9
Seismogram
$ phase
19:23:04.7
8
" phase
19:23:07.5
3
'%pocenter (Distance)
Reading Maximum
#mplitude
Determination
of magnitude
Reading arrival time
of $ phase * " phase
Determination
of '%pocenter
Maximum amplitude
15.3mm
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9-wave :rst motions
"!is type more likely to produce large tsunamis
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Harvard;/$3 *oment "ensor Solutions
7/23/2019 Session I.4 Yamamoto
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Haskell %ine SourceDislocation Source
8askell* $,52sumatra
Sumatra eart!&uake 3s!ii et al64
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omplicated Slip Distributions
9
,000 !i-!i4 "aiwan $art!&uake
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Single-force eart!&uakesvolcanic eruptions and landslides
*ount St6 Helens4 >S. ?anamori et al6 ,071
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$art!&uake Si+e @ *agnitude
* A log . @ log .2 ic!ter4 ,0=7
!arles ic!ter,022-,07=
log of amplitudeDistance correction
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*agnitude Determination
Magnitude+ "i,e of Earth-ua!e
(Defined .% Richter (/012) at first)
M3log/4(#mplitude)5(Correction for Distance)
#mplitude47/ M
#mplitude/4 M
#mplitude/44 M
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*% %ocal magnitude (alifornia) regional S and 26,-,
surface waves
* C*. (Capan *eteorol6 .gency) regional S and =-,2 s
surface waves
mb Body wave magnitude teleseismic 9 waves
*s Surface wave magnitude teleseismic surface
waves*w *oment magnitude teleseismic surface
7/23/2019 Session I.4 Yamamoto
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*agnitudes for t!e Sumatra $art!&uake
mb 562 , sec 9 wave ,E, station
mblg 865 , sec %g waves 8 station
*wp 762 @ 76= 82 sec 9 waves
*s 76= - 767
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elations!ip between dierent types of magnitudes
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Seismic *oment A (igidity)(.rea)(Slip)
$art!&uake si+e - Seismic *oment
.rea (.)
Slip (S)
3737 tuStM =
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*wp 9-wave moment magnitude
Guick magnitude from 9 wave >ses relatively long-period body waves (,2-82 Some problems for *762
*oA *a Iu+(t)dtI 1Er;Fp
*wA (log,2*o@ 06,);,6=
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*wp 9-wave moment magnitude
u+(t)dt J *o
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Seismic moments and fault areasof some famous eart!&uakes
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$art!&uake *agnitude and"sunami
Ground
Length
Displa
cement
*agnitude
Displacement(m)
%engt!(km)
E 262E 2611 2627 ,61
= 26
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*agnitude and "sunami
8ater volume lifted .% the fault motion(#rea)(Displacement)
Magnitude 5/
;
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upture 9ropagationRupture :elocit% < "&ave "peed
Duration of Rupture3 Fault ;engthRupture :elocit%
Magnitude =
Duration 3 (24!m)(1!ms)
3/4and several (sec)
Magnitude
?
Duration 3 (/44
/24
)
1!ms 314 (sec)
/(min)
Earth-ua!e on Dec7 96 944@
Rupture :elocit% 9!ms
Duration > /4 min
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*agnitudes for "sunami 'arnings
'ant to know t!e moment (fault area and si+e) but takes a long time (!ours) to collect surface wav or free oscillation data
*agnitude from 9 waves (mb) is fast butunderestimates moment
3f !ave time (!ours)4determine *mfrom mantle waves
K For &uick magnitude (seconds to minutes)4
determine *wpfrom 9 waves
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"!ings to emember
,6 $art!&uake sources are a double couple force syst w!ic! is e&uivalent to Fault Slip
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"sunami *agnitude
Distant tsunami (A> /444 !m)Mt3log/4'5C507/
C+ Correction constant7
;ocal tsunamiMt3log/4'5log/4A527?4
'+ Tsunami height (m)7
A+ Epicentral distance (!m)+
/44 !m A 1+244 !m7 (#.e+ /0=0+ /0?/)
7>sed to e1press si?e of tsunami effect.3
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"!ank you for yourattention
Chang 8eng ASeismometerB #4$&)
7/23/2019 Session I.4 Yamamoto
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iuseppe (ercalli
7$%-9$,$23@ohn (ilne
7$%-9$,$&3
g g
Sassa Seismometer 7$,&-3* #buyama* !yoto >niv.
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"!e SourceFault mec!anisms
"!e S!aking'ave propagationStructures
'!at is an $art!&uake
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$lastic ebound "!eory eid (,0,2)
74ata in $%-$95-* $%+29,)* $,53
%.- feet offset in San #ndreas fault
from $,5 earthquake. (irin County
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Singleouple Double ouple
Single ouple versus Double ouple
9 polarity pattern same
S polarity pattern diferent
Single ouple LresemblesM fault slip
ontroversy settledby *aruyama (,08E)
S!owed t!at Doubleouple was e&uivalento fault slip
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$&uivalent Body Forces
Single Force
Dipole
ouple(Single ouple)
Double ouple
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*oment tensor dipoles and couples
7 3 7 * 3 7 3pq q pV
M t f t dV= B B
7L= p.&2&D #R p.-3
0 componentsSymmetric matri so 8 independent
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&))&&$$&)$$) ====== MMMMMM
&&))$$ MMM ==
*oment "ensor for an $plosion
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)$$) MM =
&$$&)&)&&&))$$ ======= MMMMMMM
Double ouple Fault - Slip
*oment "ensor for Fault Slip
/ort!
i l k S t d Hi ,05E
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ircular rack @ Sato and Hirasawa4 ,05E
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*m *antle *agnitude
*mA log,2(N()) O d O s @ E60
Distanceorrection
Source orrection
Spectral .mplitude
amplitude measured in fre&uency domain surface waves wit! periods
7/23/2019 Session I.4 Yamamoto
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1944 TonankaiMw 81
,018 /ankai
*w 76,
,00=?obe
*w 860
Fault .reas ofDamaging $art!&uakes
Deat!s
,011 ,
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Seismicity in /$3 catalog ,002 -
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Fault areas of somefamous eart!&uakes
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adiated $nergy A ,6=*wO ,,67
Seismic adiated $nergy
?anamori4 ,055
" f * it d S l
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*% %ocal magnitude (alifornia) regional S and 26,-,surface waves
* C*. (Capan *eteorol6 .gency) regional S and =-,2 s
surface waves
mb Body wave magnitude teleseismic 9 waves
*s Surface wave magnitude teleseismic surface
waves
*w *oment magnitude teleseismic surface < waves*wp 9-wave moment magnitude teleseismic 9 waves ,2
*m *antle magnitude teleseismic surface