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![Page 1: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/1.jpg)
Overview of lectureOverview of lecture
• Acquisition of Data• Measures of ground motion• Processing of Data• Properties of Data from Observations
– Data distribution in M-D space– Path dependence of ground motion– Magnitude dependence of ground motion– Site dependence of ground motion
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The first known instrument for earthquakes measurement is the Chang seismoscope built in China in 132 B.C.
Balls were held in the dragons’ mouths by lever devices connected to an internal pendulum. The direction of the epicenter was reputed to be indicated by the first ball released.
MEASURING EARTHQUAKES
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Jargon
seismoscope – an instrument that documents the occurrence of ground motion (but does not record it over time)
seismometer – an instrument that senses ground motion and converts the motion into some form of signal
accelerometer – a seismometer that records acceleration, also known as strong ground motion
geophone – another name for a seismometer, commonly used in active source seismology
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More Jargon
seismograph – a system of instruments that detects and records ground motion as a function of time
seismogram – the actual record of ground motion produce by a seismograph
seismometry – the design and development of seismic recording systems
data logger – device that converts analog to digital signal and stores the signal
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How Seismometers Work
Fundamental Idea: To record ground motion a seismometer must be decoupled from the ground. If the seismometer moves with the ground then no motion will be recorded.
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Principles of seismographs
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Strong-Motion Accelerographs
Analog
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Magnification curves
Not shown: broadband (0.02—DC sec)
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The nature of the seismogram and the waves shown depends directly on the type
of seismograph
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It is easier to make a stable, small short-period oscillator than a long-period oscillator. Note that modern strong-motion sensors use force-balance accelerometers with resonant frequencies near 50 Hz, where the quantity being measured is the current in a coil required to keep the mass centered. This current is proportional to the force on the mass.
“Broadband” seismometers (velocity sensors, using electronics to extend the frequency to low values) are starting to be used in engineering seismology: the boundary between traditional strong-motion and weak-motion seismology is becoming blurred.
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Digital strong-motion recording
• Broadband: nominally flat response from dc to at least 40 Hz– But noise/ baseline problems can limit low-frequency
information– High-frequency limit generally not a problem because these
frequencies are generally filtered out of the motion by natural processes (exception: very hard rock sites)
• High dynamic range (ADC 16 bits or higher)• Pre-event data usually available
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Trifunac &
Todorovska (2001)
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Many networks of instruments, both traditional “strong-motion” and, more
recently, very broad-band, high dynamic-range sensors and dataloggers
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http://www.k-net.bosai.go.jp
• 1000 digital instruments installed after the Kobe earthquake of 1995
• free field stations with an average spacing of 25 km
• velocity profile of each station up to 20 m by downhole measurement
• data are transmitted to the Control Center and released on Internet in 3-4 hours after the event
INSTRUMENTATION
Kyoshin Net: Japanese strong motion network
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Reminder: Play Chuettsu and Tottori movies
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A number of web sites provide data from instrument networks
• But no single web site containing data from all over the world.
• An effort is still need to add broad-band data into the more traditional data sets.
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WEB SITES
COSMOS Consortium of Organizations for Strong - Motion Observation Systems
http://www.cosmos-eq.org/
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Measures of ground-motion intensity for Measures of ground-motion intensity for engineering purposesengineering purposes
• PGA, PGV• Response spectra (elastic, inelastic)• Others (avg. spectra over freq., power
spectra, Fourier amplitude spectra)• Time series
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Peak ground acceleration (pga)• easy to measure because the response of most
instruments is proportional to ground acceleration
• liked by many engineers because it can be related to the force on a short-period building
• convenient single number to enable rough evaluation of importance of records
• BUT it is not a measure of the force on most buildings
• and it is controlled by the high frequency content in the ground motion (i.e., it is not associated with a narrow range of frequencies); records can show isolated short-duration, high-amplitude spikes with little engineering significance
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Peak ground velocity (pgv)
• Many think it is better correlated with damage than other measures
• It is sensitive to longer periods than pga (making it potentially more predictable using deterministic models)
• BUT it requires digital processing (no longer an important issue)
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Peak ground displacement (pgd)
• The best parameter for displacement-based design?• BUT highly sensitive to the low-cut (high-pass) filter that
needs to be applied to most records (in which case the derived pgd might not represent the true pgd, unlike pga, for which the Earth imposes a natural limit to the frequency content). For this reason I recommend against the use of pgd.
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Äug
Elastic response spectra (many structures Elastic response spectra (many structures can be idealized as SDOF oscillators)can be idealized as SDOF oscillators)
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10 20 30 40 50 60
-100
1020
Time (sec)
-5
0
5
0.1 1 10 100
10-4
0.001
0.01
0.1
1
10
100
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
1999 Hector Mine Earthquake (M 7.1)
station 596 (r= 172 km), transverse component
Ground acceleration (cm/sec2)
Ground displacement (cm)
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10 20 30 40 50 60
-100
1020
Time (sec)
-5
0
5
0.1 1 10 100
10-4
0.001
0.01
0.1
1
10
100
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
1999 Hector Mine Earthquake (M 7.1)
station 596 (r= 172 km), transverse component
10 20 30 40 50 60
-2*10 -4
0
2*10 -4
Time (sec)
Tosc = 0.025 sec
Ground acceleration (cm/sec2)
Ground displacement (cm)
At short periods, oscillator response proportional to base acceleration
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10 20 30 40 50 60
-100
1020
Time (sec)
-5
0
5
-0.001
0
0.001
0.1 1 10 100
10-4
0.001
0.01
0.1
1
10
100
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
1999 Hector Mine Earthquake (M 7.1)
station 596 (r= 172 km), transverse component
10 20 30 40 50 60
-2*10 -4
0
2*10 -4
Time (sec)
Tosc = 0.025 sec
Tosc = 0.050 sec
Ground acceleration (cm/sec2)
Ground displacement (cm)
![Page 29: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/29.jpg)
10 20 30 40 50 60
-100
1020
Time (sec)
-5
0
5
-0.001
0
0.001
-1
0
1
0.1 1 10 100
10-4
0.001
0.01
0.1
1
10
100
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
1999 Hector Mine Earthquake (M 7.1)
station 596 (r= 172 km), transverse component
10 20 30 40 50 60
-2*10 -4
0
2*10 -4
Time (sec)
Tosc = 0.025 sec
Tosc = 0.050 sec
Tosc = 1.0 sec
Ground acceleration (cm/sec2)
Ground displacement (cm)
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10 20 30 40 50 60
-100
1020
Time (sec)
-5
0
5
-0.001
0
0.001
-1
0
1
-10
0
10
0.1 1 10 100
10-4
0.001
0.01
0.1
1
10
100
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
1999 Hector Mine Earthquake (M 7.1)
station 596 (r= 172 km), transverse component
10 20 30 40 50 60
-2*10 -4
0
2*10 -4
Time (sec)
Tosc = 0.025 sec
Tosc = 0.050 sec
Tosc = 1.0 sec
Tosc = 10 sec
Ground acceleration (cm/sec2)
Ground displacement (cm)
![Page 31: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/31.jpg)
10 20 30 40 50 60
-100
1020
Time (sec)
-5
0
5
-0.001
0
0.001
-1
0
1
-10
0
10
-5
0
5
0.1 1 10 100
10-4
0.001
0.01
0.1
1
10
100
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
1999 Hector Mine Earthquake (M 7.1)
station 596 (r= 172 km), transverse component
10 20 30 40 50 60
-2*10 -4
0
2*10 -4
Time (sec)
Tosc = 0.025 sec
Tosc = 0.050 sec
Tosc = 1.0 sec
Tosc = 10 sec
Tosc = 40 sec
Ground acceleration (cm/sec2)
Ground displacement (cm)
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10 20 30 40 50 60
-100
1020
Time (sec)
-5
0
5
-0.001
0
0.001
-1
0
1
-10
0
10
-5
0
5
0.1 1 10 100
10-4
0.001
0.01
0.1
1
10
100
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
1999 Hector Mine Earthquake (M 7.1)
station 596 (r= 172 km), transverse component
10 20 30 40 50 60
-2*10 -4
0
2*10 -4
Time (sec)
-5
0
5
Tosc = 0.025 sec
Tosc = 0.050 sec
Tosc = 1.0 sec
Tosc = 10 sec
Tosc = 40 sec
Tosc = 80 sec
Ground acceleration (cm/sec2)
Ground displacement (cm)
At long periods, oscillator response proportional to base displacement
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0.1 1 10 100
0.01
0.1
1
10
100
Period (sec)
Acc
eler
atio
n(c
m/s
2)
0.1 1 10 100
10-4
0.001
0.01
0.1
1
10
100
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
1999 Hector Mine Earthquake (M 7.1)
station 596 (r= 172 km), transverse component
convert displacement spectrum into acceleration spectrum (multiply by (2π/T)2)
Acceleration spectrum usually used in engineering
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0.1 1 10 1000.001
0.01
0.1
1
10
100
Period (sec)
2% damping5% damping10% damping20% damping F
ile:
C:\
en
cy
clo
pe
dia
_b
om
me
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d_
4_
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ate
:20
03
-09
-09
;Tim
e:
16
:03
:19
20 40 60 80 100
5
10
15
20
25
Period (sec)
Rel
ativ
eD
ispl
acem
ent
(cm
)
2% damping5% damping10% damping20% damping
1999 Hector Mine Earthquake (M 7.1)station 596 (r= 172 km), transverse component
At short and very long periods, damping not significantAt short and very long periods, damping not significant
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PGA generally a poor measure of ground-motion intensity. All of these time series have the same PGA:
0 50 100 150-0.2
-0.1
0
0.1
0.2
Acc
eler
atio
n(g
) Peru, 5 Jan 1974, Transverse Comp., Zarate
M = 6.6, rhyp = 118 km
0 50 100 150-0.2
-0.1
0
0.1
0.2
Acc
eler
atio
n(g
) Montenegro, 15 April 1979, NS Component, Ulcinj
M = 6.9, rhyp = 29 km
0 50 100 150-0.2
-0.1
0
0.1
0.2A
ccel
erat
ion
(g) Mexico, 19 Sept. 1985, EW Component, SCT1
M = 8.0, rhyp = 399 km
0 50 100 150-0.2
-0.1
0
0.1
0.2
Time (sec)
Acc
eler
atio
n(g
) Romania, 4 March 1977 EW Component, INCERC-1M = 7.5, rhyp = 183 km
File
:D
:\e
nc
yc
lop
ed
ia_
bo
mm
er\
ac
ce
l_s
am
e_
pg
a.d
raw
;Da
te:2
00
5-0
4-2
0;T
ime
:1
9:4
4:3
3
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0.1 1 1010-5
10-4
0.001
0.01
0.1
1
Period (sec)
Peru (M=6.6,rhyp=118km)
Montenegro (M=6.9,rhyp=29km)
Mexico (M=8.0,rhyp=399km)
Romania (M=7.5,rhyp=183km)
File
:D
:\e
ncy
clo
pe
dia
_b
om
me
r\p
sa_
sam
e_
pg
a.d
raw
;D
ate
:2
00
5-0
4-2
0;T
ime
:1
9:3
4:1
6
0 2 4 6 8 100
0.2
0.4
0.6
0.8
1
Period (sec)
5%-D
ampe
d,P
seud
o-A
bsol
ute
Acc
eler
atio
n(g
)
Peru (M=6.6,rhyp=118km)
Montenegro (M=6.9,rhyp=29km)
Mexico (M=8.0,rhyp=399km)
Romania (M=7.5,rhyp=183km)
But the response spectra (and consequences for structures) are quite different (lin-lin and log-log plots to emphasize different periods of motion):
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Data Processing
• Data processing = removing long-period noise• Processing at high frequencies of much less concern
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Baseline problems are common
• Even for digitally recorded records• There can be many reasons for the shifts, and as a
result it is not possible to design a single correction scheme to remove the long-period noise without affecting the long-period signal.
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-300
0
300
cm/s
ec2 Acceleration
-50
0
cm/s
ec
Velocity
0 20 40 60
-500
0
Time (s)
cm
Displacement
1999 Hector Mine (M=7.1), HEC, E-W (rjb=8.2 km)
File
:C
:\psv
\Pro
cpa
pr\
He
cea
vdl.d
raw
;D
ate
:2
00
3-0
9-1
0;
Tim
e:
14
:13
:39
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Many possible causes
• Mechanical:– Hysteresis (mechanical/ electrical)– “Popcorn” noise– Other
• Ground deformation– Tilt near earthquakes– Differential settlement– Other
• Analog-Digital Conversion (ADC)
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• Seismologists may want residual displacements. Schemes have been tailored that claim to produce these. Although OK in some cases of large signal to noise, in general I am pessimistic about being to remove long-period noise and retain long-period signal.
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A possible correction scheme
• Modification of one proposed by Iwan et al. (1985)
• Guarantees that velocity will have a value around 0.0 in the later part of the record (a physical constraint)
• Choice of critical parameters is arbitrary unless they can be associated with a physical mechanism (as for the specific instrument studied by Iwan et al.)
![Page 43: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/43.jpg)
20 40 60 80
-50
0
50
Time (sec)
Vel
ocity
(cm
/sec
)
TCU129, E-W
t1
t2=30 sec
t2=50 sec
t2=70 sec
File
:C
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0 20 40 60 80 100-200
0
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Dis
pla
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t(c
m)
TCU129, E-W
t2 = 30 sec
t2 = 50 sec
t2 = 70 sec
GPS, station AF11
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:09
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Although the results look physically plausible, the residual displacements can be sensitive to
t1, t2
![Page 45: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/45.jpg)
• But response spectra at periods of engineering interest can be insensitive to the baseline correction, which says that the “noise” is very long period
• If abandon desire to recover residual displacements, then many methods are available for removing long-period noise, in addition to baseline correction: filtering, polynomial fits, combinations of above.
![Page 46: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/46.jpg)
0 20 40 60 80 100-200
0
200
400
Time (sec)
Dis
pla
cem
en
t(c
m)
TCU129, E-W
remove mean only
t2 = 30 sec
t2 = 50 sec
t2 = 70 sec
quadratic fit to velocity
low-cut filter only, fc=0.02 Hz
GPS, station AF11
File
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Although the results look physically plausible, the residual displacements can be sensitive to
t1, t2
Quadratic fit to velocity gives best fit to GPS residual displacement in this casein this case
![Page 47: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/47.jpg)
1 101 102101
102
period (s)
5%-d
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dre
lativ
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spla
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(cm
)
no adjustmentst2 = 70 st2 = 50 st2 = 30 sno bl; acausal flc=0.02
TCU129, EW
File
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• In spite of large differences in waveforms, the response spectra at periods of engineering interest are similar. Two general conclusions to be made here:– Filtering alone is often all that is needed– Response spectra at periods of engineering interest are often
insensitive to filter cutoff periods for modern digital records
![Page 49: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/49.jpg)
• More examples, comparing displacements and SD from accelerograms and “high-rate” (1 sps) gps
![Page 50: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/50.jpg)
![Page 51: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/51.jpg)
From Wang et al.
![Page 52: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/52.jpg)
From Guoquan Wang
![Page 53: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/53.jpg)
• Still have many analog records, for which choosing the filter corner can be very important if want long-period response spectra (e.g., project in Italy to determine regression equation for T=10 s SD)
![Page 54: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/54.jpg)
![Page 55: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/55.jpg)
Choosing Filter Corners
• Choosing filter corners often guided by – Shape of Fourier acceleration spectrum (look for f^2 slope)– Appearance of displacement waveforms (do they “look
reasonable”?)
![Page 56: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/56.jpg)
![Page 57: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/57.jpg)
![Page 58: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/58.jpg)
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Choosing Filter Corners
• near- and intermediate-field contributions to ground displacement can fool our ideas of what is “normal” or “reasonable”
![Page 60: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/60.jpg)
Note very different shape for EW, NS components, and peculiar shape for NS waveform until fc=0.16
Data from C. Di’Alessandro
![Page 61: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/61.jpg)
Data from C. Di’Alessandro
But data from a nearby station (2 km) shows that the “peculiar” features are real, and suggest that a filter somewhere between 0.04 and 0.08 is appropriate
![Page 62: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/62.jpg)
To convince you that differences are independent of acausal filter transients:
![Page 63: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/63.jpg)
In spite of the resemblance of the displacement traces, the response spectra are less similar than I would have expected, demonstrating that the spatial variation in ground motions can be large
![Page 64: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/64.jpg)
CharacteristicsCharacteristics of Data
• Magnitude-Distance depends on region• Change of amplitude with distance for fixed magnitude• Change of amplitude with magnitude after removing
distance dependence• Site dependence• Scatter
![Page 65: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/65.jpg)
Observed data adequate for regression exceptclose to large ‘quakes(the recently developed NGA database contains such records, primarily from Taiwan and Turkey)
Observed data not adequate for regression, use simulated data
1 10 100 1000
5
6
7
8
Mom
ent
Mag
nitu
de
Used by BJF93 for pga
Western North America
1 10 100 1000
5
6
7
8
Distance (km)
Mom
ent
Mag
nitu
de
AccelerographsSeismographic Stations
Eastern North America
File
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Path effects
• Wave types– Body (P, S)– Surface (Love, Rayleigh)
• Amplitude changes due to wave propagation– Geometrical spreading (1/r in uniform media, more rapid
decay for velocity increasing with depth)– Critical angle reflections– Waveguide effects
• Amplitude changes due to intrinsic attenuation (conversion to heat) and scattering attenuation
![Page 67: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/67.jpg)
How does the motion depend on distance?
• Generally, it will decrease (attenuate) with distance• But wave propagation in a layered earth predicts more
complicated behavior (e.g., increase at some distances due to critical angle reflections (“Moho-bounce”)
• Equations assume average over various crustal structures
![Page 68: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/68.jpg)
![Page 69: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/69.jpg)
![Page 70: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/70.jpg)
More distant data show limitations of function fit to closer data (but ground motions at greater distances are of little engineering interest)
From V. Graizer
![Page 71: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/71.jpg)
Scaling with magnitudeScaling with magnitude
![Page 72: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/72.jpg)
0.1 1 10 100
10
100
1000
10000
Rjb (set values less than 0.1 to 0.1 km)
PS
A(c
m/s
ec2)
Chi-Chi (M 7.6)Loma Prieta (M 6.9)Northridge (M 6.7)
T = 0.1 sec
0.1 1 10 100
Rjb (set values less than 0.1 to 0.1 km)
Chi-Chi (M 7.6)Loma Prieta (M 6.9)Northridge (M 6.7)
T = 2 sec
File
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Chi-Chi data are low at short periods(note also scatter, distance dependence)
Illustrating distance and magnitude dependence
![Page 73: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/73.jpg)
0.1 1 10 100
10
100
1000
10000
Rjb (set values less than 0.1 to 0.1 km)
PS
A(c
m/s
ec2)
Denali fault (M 7.9)Kocaeli (M 7.5)Northridge (M 6.7)
T = 0.1 sec
0.1 1 10 100
Rjb (set values less than 0.1 to 0.1 km)
Denali fault (M 7.9)Kocaeli (M 7.5)Northridge (M 6.7)
T = 2 sec
File
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11:5
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And so are Denali and Kocaeli (or is Northridge high?)
![Page 74: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/74.jpg)
4 5 6 7 81
2
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1
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T=0.1, 0.3, 1.0, 2.0 secrjb _< 80: buried eventsrjb _< 80: events with surface slip
File
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-05-
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:36:
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Magnitude scaling
Note that each symbol represents the average of the strong-motion recordings for a single earthquake, correcting for the distance dependence.
(note strong correlation of events breaking to the surface with magnitude)
![Page 75: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/75.jpg)
4 5 6 7 81
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T=0.1, 0.3, 1.0, 2.0 secquadratic in Mrjb _< 80: buried eventsrjb _< 80: events with surface slip
File
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fit.d
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-05-
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:36:
07Magnitude scaling
quadratic fit (used for empirical ground-motion prediction equations)
Note decrease of motion with increase of M for T = 0.1 and 0.3 sec
![Page 76: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/76.jpg)
Site Effects, Basin Waves,Spatial Variability, Site Effects, Basin Waves,Spatial Variability, Azimuthal DependenceAzimuthal Dependence
![Page 77: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/77.jpg)
People have known for a long time thatPeople have known for a long time thatmotions on soil are greater than on rockmotions on soil are greater than on rock
• e.g., Daniel Drake (1815) on the 1811-1812 New Madrid sequence:
•
– "The convulsion was greater along the Mississippi, as well as along the Ohio, than in the uplands. The strata in both valleys are loose. The more tenacious layers of clay and loam spread over the adjoining hills … suffered but little derangement."
![Page 78: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/78.jpg)
Steidl
![Page 79: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/79.jpg)
Steidl
![Page 80: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/80.jpg)
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2002 M 7.9 Denali Fault
![Page 82: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/82.jpg)
K2-16
1741
K2-03
K2-06K2-09
K2-11K2-12
K2-14
K2-22
1744
1751
K2-02
K2-13
1734
1737
K2-01
K2-04
K2-05
K2-07
K2-19
1397
1731
1736
K2-08
K2-20K2-21
-150 -149.8
61.1
61.2
Longitude (oE)
La
titu
de
(oN
)
D
C/D C
Chu
gach
Mts
.
Site Classes are based on the average shear-wave velocity in the upper 30 m (discussed later).
![Page 83: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/83.jpg)
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pulses 1 & 2: subevent 1pulse 3: subevent 2pulse 4: subevent 3
![Page 85: Overview of lecture Acquisition of Data Measures of ground motion Processing of Data Properties of Data from Observations –Data distribution in M-D space.](https://reader036.fdocuments.net/reader036/viewer/2022062717/56649e485503460f94b3b89b/html5/thumbnails/85.jpg)
0.1 1 100.001
0.01
0.1
1
10
100
Frequency (Hz)
Fou
rier
Acc
eler
atio
n(c
m/s
ec)
Denali: EWclass Dclass C/Dclass Cclass B (one site)
range of previous site response studies
0.1 1 100.1
0.2
1
2
Frequency (Hz)R
atio
(rel
ativ
eto
avg
C)
Denali: EWclass Dclass C/Dclass Cclass B (one site)
range of previous site response studies
File
:C
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_4
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;Da
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Basin Waves Basin Waves
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time (sec)
0 20 40 60 80 100
1.6
-1.73.9
-4.76.0
-5.0
b) velocity (cm/s)UP90, S3EE
SF71, PV
SF71, CM
time (sec)
0 20 40 60 80 100
0.80
-0.973.2
-2.64.2
-5.0
c) displacement (cm) UP90, S3EE
SF71, PV
SF71, CM
-- Horizontal Components --
UP90, S3EE: component x
SF71, PV: component b
SF71, CM: component a
0 20 40 60 80 100
13
-1441
-2924
-20
a) acceleration (cm/s2)
1990 Upland (M=5.6,D=74)
1971 San Fernando (M=6.6)
Palos Verdes (D=66)
Costa Mesa (D=95)
S3EE
File
:C
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:1
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0.1 0.2 1 2 10 200.1
1
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PS
V(c
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Upland (M 5.6), recorded on OBS, whole record used for PSVas above, but PSV from S-wave only.Regression: Boore etal, 1997, Vs = 216 m/sRegression: Abrahamson & Silva, 1997, corrected to 216 m/sStochastic-method simulation: AB98 model
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"Site" (path) effect
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"It is an easy matter to select two stations within 1,000 feet of each other where the average range of horizontal motion at the one station shall be five times, and even ten times, greater than it is at the other”
John Milne, (1898, Seismology)
Spatial VariabilitySpatial Variability
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Comparing the 1966 and 2004 Aftershocks
Both Earthquakes Ruptured the Same Segment
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But with Some Important Differences
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Most Extensively Observed Earthquake to Date in the Near-
Fault Region
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-120.55 -120.5 -120.45 -120.4 -120.35
35.85
35.9
35.95
36
long
lat
digital (PKD, PHOB)
analog (CSMIP)
0.17g
0.28g
1.1g
2.5 g
1.3g0.3g
10 km
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Potential Contributing Factors to the Observed Ground Motion
•Site conditions
•Rupture propagation
•Stopping phases
•Prestress (“Asperities”)
•Fault geometry
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85 90 95-400
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JFUDFU
vertical component
85 90 95
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0.05 Hz low-cut, nroll=2
85 90 95-600
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85 90 95-10
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(cm
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85 90 95-30
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Dis
(cm
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Time (s)
85 90 95
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Time (s)
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80 100 120 140
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Station 596Station 1099
Acceleration (cm/s2)
File: C:\procssng\working\596_1099_acausal_corr_avd_4ppt.draw;Date: 2005-04-18;Time: 17:31:43
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0 2 4 6 8 10
0
0.1
0.2
0.3
Interstation Spacing (km)
ofd
iffe
ren
ceo
flo
g10
ph
a
Northridge 94 MS PHA (Boore, 1997)small arrays (Abrahamson & Sykora, 1993)SMART1, f = 3.3 Hz (Abrahamson, pers. commun.)SMART1, f = 10.0 Hz (Abrahamson, pers. commun.)
2 , San Fernando (McCann & Boore, 1983)Northridge aftershocks (Field & Hough, 1997)
0 2 4 6 8 10
0
0.1
0.2
0.3
Interstation Spacing (km)
ofd
iffe
ren
ceo
flo
g10
ph
a
2*0.188 ( 1, larger comp., M6.0-6.9: Joyner, pers. commun.)
log10 pha = 0.27*(1-exp(- (0.6* ))) (eyeball fit)Chiba (Kawakami & Mogi, 2003)SMART1 (Kawakami & Mogi, 2003)SIGNAL (Kawakami & Mogi, 2003)
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END
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Azimuth-dependent amplification of weak and Azimuth-dependent amplification of weak and strong ground motions within a fault zone strong ground motions within a fault zone (Nocera Umbra, central Italy)(Nocera Umbra, central Italy)
G. Cultrera, A. Rovelli, G. Mele, R. Azzara, A. Caserta, and F. Marra (2003)
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END
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Magnitude scaling
Expected scaling for simplest self-similar model (to be discussed later)
4 5 6 7 81
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eve
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term
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1
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Me
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t_te
rm
T=0.1, 0.3, 1.0, 2.0 secrjb _< 80: buried eventsrjb _< 80: events with surface slip
File
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-2 -1 0 1 2
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Station K2-16 (filtered 0.02--0.08 Hz)
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-2 -1 0 1 2
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Station K2-20 (filtered 0.02--0.08 Hz)
24--54 s to s.e. 1
-4 -2 0 2 4
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to s.e. 2
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(K2-
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class C/Dclass D
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(K2-
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class C/Dclass D