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Effects of Strong Motion Processing Procedures on Time Histories, Elastic and Inelastic Spectra

Authors:
Paolo Bazzurro at University School for Advanced Studies IUSS Pavia
Paolo Bazzurro
Brian Sjoberg
Brian Sjoberg
Brian Sjoberg
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Nicolas Luco at United States Geological Survey
Nicolas Luco
Walter Silva
Walter Silva
Walter Silva
  • This person is not on ResearchGate, or hasn't claimed this research yet.
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Effects of Strong Motion Processing Procedures
on Time Histories, Elastic and Inelastic Spectra
By Paolo Bazzurro, Brian Sjoberg, Nicolas Luco (AIR)
Walter Silva, Robert Darragh (Pacific Engineering and Analysis)
Presented at
COSMOS INVITED WORKSHOP
ON STRONG-MOTION RECORD PROCESSING
Richmond, CA, May 26-27, 2004
www.air-worldwide.com
Motivation
To quantify on a statistical basis the effects on ground motion time
histories and elastic and inelastic spectra of
histories
and
elastic
and
inelastic
spectra
of
i. Causality of the filter
ii
Filter order
ii
.
Filter
order
iii. Selection of the high-pass cut-off frequency
iv. Preservation or removal of residual displacement offset
We considered
¾Butterworth filter only
N
(di t R
17k )
d ti f th k ith
¾
N
ea
r
-source
(di
s
t
ance
R
≤
17k
m
)
groun
d
mo
ti
ons
f
rom ear
th
qua
k
es w
ith
moment magnitude ranging from 6.5 to 7.6
¾Two components rotated fault-parallel and fault-normal
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Earthquakes and Recording Stations
Rupture Distance
S30 HP LP
X
cos(
θ
) or DMF
Earthquake Year Mag Mechanism
(k
m
)
Station Name (m/s) (Hz) (Hz)
Y
cos
(
φ
)
Imperial Valley
1979 6.5 S 8.5 Brawley Airport 209 0.10 40 0.7 1.05-1.54
1El Centro Array #6 203 0.10 40 0.5 1.00-1.08
C#
0.6 El
C
entro Array
#
7211 0.10 40 0.5 1.00-1.08
14.2 Parachute Test Site 349 0.10 40 0.7 1.05-1.54
Loma Prieta
1989 6.9 R (oblique) 6.1 LGPC 466 0.10 0.8 1.04-1.17
Landers
1992 7.3 S 1.1 Lucerne 685 0.08 60 0.63 1.03-1.36
K
obe
1995 6.9 S 10.2
Amagasaki
256 0.10 40 0.57 1.02-.123
obe
Amagasaki
0.2 Kobe University 1043 0.10 30 0.42 0.94-0.99
2.5 Port Island (0 m) 198 0.10 0.3 0.76-0.97
1.2 Takarazuka 312 0.13 33 0.64 1.03-1.39
Northridge
1994 6.7 R 6.2 Jensen Filter Plant 373 0.20 0.79 1.04-1.16
7.1 Rinaldi Receiving Stn. 282 0.10 0.77 1.03-1.15
Kocaeli, Turkey
1999 7.4 S 17 Arcelik 523 0.07 50 0.26 0.71-0.96
12.7 Duzce 276 0.08 15 0.51 1.10-1.10
17 Gebze 792 0.08 25 0.23 0.68-0.96
4.8
Izmit
811
0.10
30
0.02
0.46
-
0.92
4.8
Izmit
811
0.10
30
0.02
0.46 0.92
2.6 Yarimca 297 0.07 50 0.11 0.55-0.94
Chi-Chi, Taiwan
1999 7.6 R 4.4 TCU049 N/A 0.02 30 0.62 1.00-1.03
0.2 TCU052 N/A 0.04 50 0.61 1.00-1.02
1.1 TCU068 N/A 0.03 50 0.62 1.00-1.03
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Additional Records List
Kocaeli, Turkey
1999 7.4 S 3.1 Sakarya 471 0.04 40 0.19 0.63-0.95
Processing Techniques
2
-pole
P
2-pole/2-pole
-pole
a
ke
N
ame
A
causal 2-pole/
2
A
causal - 1.5xH
P
A
causal 2-pole/3
4
-pole
1.5xHP 4-pole
5
-pole
pole
1
.5xHP 4-pole
pole
Legend:
Earthqu
a
Station
N
Cascade
A
Cascade
A
Cascade
A
Acausal
4
Acausal -
Acausal
5
Causal 4-
Causal -
1
Causal 5-
Static
Imperial Valley
Brawley Airport H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR
El Centro Array #6 H-E06053.ATR H-E060 53.ATR H-E06 053.ATR H-E06 053.ATR H-E060 53.ATR H-E060 53.ATR H-E06 053.ATR H-E06 053.ATR H-E0 6053.A TR
El Centro Arra
y
#7 H-E0 7053.ATR H-E0 7053.ATR H-E0 7053.ATR H-E0 7053.A TR H-E070 53.A TR H-E0 7053.A TR H-E07053.A TR H-E07053.A TR H-E07053.A TR
Available
Not Available
y
Parachute Test Site H-PTS053.ATR H-PTS0 53.ATR H-PTS053.A TR H-PTS053.ATR H-PTS0 53.ATR H-PTS0 53.ATR H-PTS0 53.ATR H-PTS053 .ATR H-PTS0 53.ATR
Loma Prieta
LGPC LGP038.ATR LGP038.ATR LGP038.ATR LGP038.ATR LGP038 .ATR LGP038 .ATR LGP038 .ATR LGP038 .ATR LGP038 .ATR
Landers
Lucerne LCN175.ATR LCN175.ATR LC N175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR
Kobe
Amagasaki AMA230.ATR AMA230.ATR AMA230.ATR AMA230.ATR AM A230.ATR AM A230.ATR AMA230.ATR AMA230.ATR AMA230.ATR
Kobe University KBU2 30.ATR KBU230.ATR KBU230.A TR KBU230.ATR KBU2 30.ATR KBU230.ATR KBU230 .ATR KBU230.A TR KBU23 0.ATR
Port Island (0 m) PRI230.ATR PRI230.ATR PRI230.ATR PRI230.A TR PRI230.ATR PRI23 0.ATR PRI230.ATR PRI230.ATR PRI230.ATR
Takarazuka TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR
Nthid
N
or
th
r
id
ge
Jensen Filter Plan
t
JEN122.ATR JEN122.A TR JEN122.ATR JEN122.ATR JEN122.ATR JEN122.ATR JEN122.ATR JEN122.ATR JEN122.ATR
Rinaldi Receiving Stn. RRS122.ATR RR S122 .ATR R RS122.A TR RRS122 .ATR RR S122 .ATR RRS122 .ATR R RS122.A TR RRS122 .ATR R RS122.A TR
Kocaeli, Turkey
Arcelik ARC000.ATR ARC000.ATR ARC000.ATR ARC0 00.ATR ARC000.ATR ARC000.ATR ARC0 00.ATR ARC000.ATR ARC000.ATR
Duzce DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR
Gebze GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR
Izmit IZT0 90.ATR IZT090.ATR IZT09 0.ATR IZT090.A TR IZT09 0.ATR IZT09 0.ATR IZT090.A TR IZT090 .ATR IZT090.ATR IZT004.ATR
Yarimca YPT000.ATR Y PT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT004.ATR
Sakarya
*
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
* Parallel component only
Sakarya
SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR
Chi-Chi, Taiwan
TCU049 TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR
TCU052 TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR
TCU068 TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR
Response to Butterworth Filters of Different Orders
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Inelastic Displacement Response Spectra – What’s R?
Earthquake
A
ccelerogra
m
-
0.6
-0.4
-0.2
0
0.2
0.4
0.6
Δmax (inelastic)
(R = 4)
Δ
max (elastic)
Displacement
Response
-0.8
0.6
0246810121416
5
10
15
20
max
(elastic)
Δmax
Response
Time History
(T
n
= 1.0 sec)
-10
-5
0
0 2 4 6 8 10121416
Displaced
Structure
Base
Shea
r
dy =
Δmax (elastic)
/ R
Displacement
dy
Yield
Strength
Single
-
Degree
-
of
-
Freedom
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Δmax (elastic) Δmax (inelastic)
Single Degree of Freedom
Structure
Effects of Causality of the Filter
R=1 (Elastic)
Bandwidth upper bound
f l filt
f
or acausa
l
filt
e
r
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Bandwidth for cascade
acausal filter
Bandwidth upper bound for
causal filter
Effects of Causality of the Filter
R=8 (Severely Inelastic)
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of Filter Order: 4-pole vs. 5-pole Causal
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of Filter Order: 4-pole vs. 5-pole Acausal
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of Filter Order: 2p-2p vs. 2p-3p Acausal
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of HP cut-off frequency:
fHP vs. 1.5fHP --- 4-poleCausal Filter
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of HP cut-off frequency:
fHP vs. 1.5fHP --- 4-pole Acausal Filter
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of HP cut-off frequency:
fHP vs. 1.5fHP ---2p-2pCascade Acausal Filter
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
~5s 1.5s
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of HP cut-off frequency:
fHP vs. 1.5fHP ---2p-2pCascade Acausal Filter
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
0.5s 2.0s
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of HP cut-off frequency:
fHP vs. 1.5fHP ---2p-2pCascade Acausal Filter
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
1.0s 3.0s
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Effects of Residual Displacement
R=1 (Elastic) R=8 (Severely Inelastic)
R=1
(Elastic)
R=8
(Severely
Inelastic)
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
Notes: 1) normal components
2) 6 records only
3) Results for causal filters are similar
Summary of Effects of Processing Techniques on
Elastic and Inelastic Spectra
In general, effects are larger
¾for inelastic than for elastic spectra and
¾for longer periods at any given response level (i.e., R=1 through 8)
Causality of the filter does not systematically affect the amplitude of the spectra.
The statistical impact on spectra due to the filter order is negligible
I i th l f th HP t
ff f
f
t
ilti
t
I
ncreas
i
ng
th
e va
l
ue o
f
th
e
HP
cu
t
-o
ff
f
requency,
f
HP, genera
t
es
i
ne
l
as
ti
c spec
t
ra
that are systematically lower at periods much lower than 1/ fHP regardless of the
causality of the filter. This can be in part explained by the lengthening of the
effective period of vibration of structures in the post-elastic regime.
Records with residual displacement offset preserved generate inelastic response
spectra that are consistently higher than those caused by records with offset
removed. (Phenomenon observed for 6 fault-normal records only).
NOTE: See paper for effects on spectra caused by applying a filter to
simulated ground motion records
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
simulated
ground
motion
records
Summary of Effects of Processing Techniques on
Ground Motion TH’s
In general, effects are significant for PGD and, to a lesser extent, for PGV. The
im
p
act on other
p
arameters
(
e.
g
., PGA, Arias Intensit
y
, and duration
)
is
pp(g y )
negligible.
Causally filtered records have PGV and PGD values that are, on average,
smaller (by 5-10% and 5-15%, respectively) than those of acausally filtered
ones.
Acausally filtered records generally display a more prominent ramp of
increasing displacement prior to the onset of strong-motion than causally
filtered records Peak
-
to
-
peak displacement amplitude however is similar for
filtered
records
.
Peak
-
to
-
peak
displacement
amplitude
,
however
,
is
similar
for
each processing technique.
The filter order does not affect the ground motion parameters considered here.
Increasing the value of the HP cut
-
off frequency
f
HP
generates records with
Increasing
the
value
of
the
HP
cut
off
frequency
,
f
HP
,
generates
records
with
lower PGV and PGD values (5% and 15-20%, respectively), as expected.
The values of PGV and PGD are considerably larger (5-20% and 50-60%,
respectively) in records with residual static offset preserved, as expected.
© 2004 AIR Worldwide Corporation COSMOS WORKSHOP
... Although these studies revealed versatile information about the reliable long-period spectral range for elastic oscillator response, they did not extend their observations to nonlinear oscillator response. Boore and Akkar (2003) and Bazzurro et al. (2005) conducted limited studies about the influence of different filtering types (causal vs. acausal) on the calculation of inelastic spectrum. These studies concluded that inelastic spectrum is less sensitive to the low-cut filter values when bi-directional (acausal) filters are used. ...
... Although these studies revealed versatile information about the reliable long-period spectral range for elastic oscillator response, they did not extend their observations to nonlinear oscillator response. Boore and Akkar (2003) and Bazzurro et al. (2005) conducted limited studies about the influence of different filtering types (causal vs. acausal) on the calculation of inelastic spectrum. These studies concluded that inelastic spectrum is less sensitive to the low-cut filter values when bi-directional (acausal) filters are used. ...
INFLUENCE OF LOW-CUT FILTER FREQUENCY ON NONLINEAR OSCILLATOR DISPLACEMENTS COMPUTED FROM NON-DEGRADING TO DEGRADING HYSTERETIC MODELS
Conference Paper
Full-text available
  • Jan 2008
Low-cut filtering used for removing the long-period noise in accelerograms is investigated for its effects on the nonlinear peak oscillator displacements. We used a suite of analog and digital accelerograms from Turkish strong-motion database and low-cut filtered each record by a set of randomly generated filter cutoffs. We computed nonlinear displacement spectra to highlight the period-dependent influence of low-cut filtering on the nonlinear oscillator response. Differences in the nonlinear oscillator response are considered by using a wide range of hysteretic models that cover non-degrading to severely degrading structural behavior. Our analyses show that inelastic spectral displacements are more vulnerable to low-cut filtering than their elastic counterparts. This can be attributed to the intricate relation between the nonlinear structural parameters, record quality and ground-motion features that increase the level of complexity between the nonlinear oscillator response and low-cut filtering. Recording type (digital / analog recording), earthquake magnitude, site classification, inelasticity level, hysteretic model as well as the variations in peak ground motion are the prominent factors about the influence of low-cut filters on peak nonlinear oscillator displacements. KEYWORDS: record processing, nonlinear oscillator response, non-degrading / degrading hysteretic behavior, constant strength and ductility spectrum, probability
View
... Acausal filtering is achieved by running a causal Butterworth filter forward and then backward in the time domain. In strong-motion processing, acausal filtering is generally preferred over causal filtering to avoid phase distortion in the signal (Boore and Akkar, 2003;Bazzurro et al., 2005); causal filtering is not an option in PRISM. The acausal filter is applied in the time domain by convolution of its transform with the time history. ...
PRISM Software: Processing and Review Interface for Strong‐Motion Data
Article
A continually increasing number of high-quality digital strong-motion records from stations of the National Strong Motion Project (NSMP) of the U.S. Geological Survey, as well as data from regional seismic networks within the United States, calls for automated processing of strong-motion records with human review limited to selected significant or flagged records. The NSMP has developed the Processing and Review Interface for Strong Motion data (PRISM) software to meet this need. In combination with the Advanced National Seismic System Quake Monitoring System (AQMS), PRISM automates the processing of strong-motion records. When used without AQMS, PRISM provides batch-processing capabilities. The PRISM software is platform independent (coded in Java), open source, and does not depend on any closed-source or proprietary software. The software consists of two major components: a record processing engine composed of modules for each processing step, and a review tool, which is a graphical user interface for manual review, edit, and processing. To facilitate use by non-NSMP earthquake engineers and scientists, PRISM (both its processing engine and review tool) is easy to install and run as a stand-alone system on common operating systems such as Linux, OS X, and Windows. PRISM was designed to be flexible and extensible to accommodate implementation of new processing techniques. All the computing features have been thoroughly tested.
View
... Acausal filtering is achieved by running a causal Butterworth filter forward and then backward in the time domain. In strong-motion processing, acausal filtering is generally preferred over causal filtering to avoid phase distortion in the signal (Boore and Akkar, 2003;Bazzurro et al., 2005); causal filtering is not an option in PRISM. The acausal filter is applied in the time domain by convolution of its transform with the time history. ...
PRISM Software: Processing and Review Interface for Strong-Motion Data
Article
A continually increasing number of high-quality digital strong- motion records from stations of the National Strong Motion Project (NSMP) of the U.S. Geological Survey, as well as data from regional seismic networks within the United States, calls for automated processing of strong-motion records with human review limited to selected significant or flagged records. The NSMP has developed the Processing and Review Interface for Strong Motion data (PRISM) software to meet this need. In combination with the Advanced National Seismic System Quake Monitoring System (AQMS), PRISM automates the processing of strong-motion records. When used without AQMS, PRISM provides batch-processing capabilities. The PRISM software is platform independent (coded in Java), open source, and does not depend on any closed-source or proprietary software. The software consists of two major components: a record processing engine composed of modules for each processing step, and a review tool, which is a graphical user interface for manual review, edit, and processing. To facilitate use by non-NSMP earthquake engineers and scientists, PRISM (both its processing engine and review tool) is easy to install and run as a stand-alone system on common operating systems such as Linux, OS X, and Windows. PRISM was designed to be flexible and extensible to accommodate implementation of new processing techniques. All the computing features have been thoroughly tested.
View
... The sensitivity to filtering method presented by Pacific Engineering at the NGA-COSMOS joint working group meeting showed that for most of the nearly 1000 components studied the elastic response spectra differences associated with the different filtering methods are small and they do not appear to result in systematic high or low bias of spectra within the common pass band. Bazzurro et al. (2004), in another large spectral domain study, support the above observation. They found that elastic and inelastic spectra from causal and acausal filtered records are statistically indistinguishable from each other provided the same filter order and corner frequencies have been used. ...
NGA Project Strong-Motion Database
Article
Full-text available
A key component of the NGA research project was the development of a strong-motion database with improved quality and content that could be used for ground-motion research as well as for engineering practice. Development of the NGA database was executed through the Lifelines program of the PEER Center with contributions from several research organizations and many individuals in the engineering and seismological communities. Currently, the data set consists of 3551 publicly available multi-component records from 173 shallow crustal earthquakes, ranging in magnitude from 4.2 to 7.9. Each acceleration time series has been corrected and filtered, and pseudo absolute spectral acceleration at multiple damping levels has been computed for each of the 3 components of the acceleration time series. The lowest limit of usable spectral frequency was determined based on the type of filter and the filter corner frequency. For NGA model development, the two horizontal acceleration components were further rotated to form the orientation-independent measure of horizontal ground motion (GMRotI50). In addition to the ground-motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record was also developed. NGA data have been systematically checked and reviewed by experts and NGA developers.
View
Processing and Review Interface for Strong Motion Data (PRISM)—Methodology and Automated Processing, Version 1.0.0
Technical Report
Full-text available
  • Feb 2017
A continually increasing number of high-quality digital strong-motion records from stations of the National Strong-Motion Project (NSMP) of the U.S. Geological Survey (USGS), as well as data from regional seismic networks within the United States, call for automated processing of strong-motion records with human review limited to selected significant or flagged records. The NSMP has developed the Processing and Review Interface for Strong Motion data (PRISM) software to meet this need. In combination with the Advanced National Seismic System Quake Monitoring System (AQMS), PRISM automates the processing of strong-motion records. When used without AQMS, PRISM provides batch-processing capabilities. The PRISM version 1.0.0 is platform independent (coded in Java), open source, and does not depend on any closed-source or proprietary software. The software consists of two major components: a record processing engine and a review tool that has a graphical user interface (GUI) to manually review, edit, and process records. To facilitate use by non-NSMP earthquake engineers and scientists, PRISM (both its processing engine and review tool) is easy to install and run as a stand-alone system on common operating systems such as Linux, OS X, and Windows. PRISM was designed to be flexible and extensible in order to accommodate new processing techniques. This report provides a thorough description and examples of the record processing features supported by PRISM. All the computing features of PRISM have been thoroughly tested.
View
Engineering Characterization of Earthquake Ground Motions
Chapter
  • Nov 2014
SynonymsAcceleration time series; Processing procedure; Strong ground motion parameters; Strong-motion databaseIntroductionA knowledge of the seismic ground motion is essential to understanding the earthquake behavior of structures. The basic data of earthquake engineering are the records of ground acceleration during moderate-to-strong earthquakes (Housner 1970). Acceleration time series (also known as accelerograms and strong-motion records) are the acceleration of the ground sampled many dozens of times per second in three mutually orthogonal directions. For decades, the reference ground motion for earthquake engineers was the renowned El Centro accelerogram, recorded in California in 1940. It was only after the Loma Prieta (1989), Northridge (1994), and Kobe (1995) earthquakes that hundreds of strong-motion records were made available worldwide through databases accessible from the Internet (Pacor et al. 2011). The huge increase of accelerograms highlights the significant variabili ...
View
PEER NGA-East Database
Technical Report
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This report serves as a documentation of the ground motion database development for the NGA-East Project. The ground motion database includes the two- and three-component ground-motion recordings from numerous selected events (M > 2.5, distances up to 1500 km) recorded in the Central and Eastern North America (CENA) region since 1988. The final database contains over 29,000 records from 81 earthquake events and 1379 recording stations. The time series and metadata collected went through numerous rounds of quality assurance and review. The NGA-East database constitutes the largest database of processed recorded ground motions in Stable Continental Regions (SRCs). The motivation behind the development of the empirical database is the same as for other NGA projects (NGA-West1 and NGA-West2), which is to be used, along with other information and data, for the development of ground motion prediction equations (GMPEs). The NGA-East ground motion database, similar to those from the NGA-West projects, includes pseudo-spectral acceleration (PSA) for the 5%-damped elastic oscillators with periods ranging from 0.01 to 10 sec. The preferred PSA measure used for the NGA-East GMPE development is RotD50, which is also provided for the same period range. Additionally, the NGA-East database includes Fourier amplitude spectral (FAS) of the processed ground motions. The NGA-East database therefore consists of three groups of complementary products: the summary file referred to as the flatfile, which contains metadata, ground motion information and intensity measures on a record-per-record basis, the time series (acceleration, velocity, and displacement), and the corresponding Fourier spectra files. The primary objective of the database task was to provide the time series, response spectra, and Fourier spectra to the NGA-East GMPE developers. However, the NGA-East time series database will also be made available to the public through the PEER online ground motion tool. This report documents the data collection, processing, and development of data products for the NGA-East database.
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Displacements, damage measures and response spectra obtained from a synthetic accelerogram processed by causal and acausal Butterworth filters
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The aim of this study is to investigate the reliability of strong motion records processed by causal and acausal Butterworth filters in comparison to the results obtained from a synthetic accelerogram. For this purpose, the fault parallel component of the Bolu record of the Duzce earthquake is modeled with a sum of exponentially damped sinusoidal components. Noise-free velocities and displacements are then obtained by analytically integrating the synthetic acceleration model. The analytical velocity and displacement signals are used as a standard with which to judge the validity of the signals obtained by filtering with causal and acausal filters and numerically integrating the acceleration model. The results show that the acausal filters are clearly preferable to the causal filters due to the fact that the response spectra obtained from the acausal filters match the spectra obtained from the simulated accelerogram better than that obtained by causal filters. The response spectra are independent from the order of the filters and from the method of integration (whether analytical integration after a spline fit to the synthetic accelerogram or the trapezoidal rule). The response spectra are sensitive to the chosen corner frequency of both the causal and the acausal filters and also to the inclusion of the pads. Accurate prediction of the static residual displacement (SRD) is very important for structures traversing faults in the near-fault regions. The greatest adverse effect of the high pass filters is their removal of the SRD. However, the noise-free displacements obtained by double integrating the synthetic accelerogram analytically preserve the SRD. It is thus apparent that conventional high pass filters should not be used for processing near-fault strong-motion records although they can be reliably used for far-fault records if applied acausally. The ground motion parameters such as ARIAS intensity, HUSID plots, Housner spectral intensity and the duration of strong-motion are found to be insensitive to the causality of filters.
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Validation of Ground-Motion Simulations for Historical Events Using SDoF Systems
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  • Dec 2012
SUMMARY The study presented in this paper addresses the issue of engineering validation of Graves and Pitarka's (2010) hybrid broadband ground motion simulation methodology with respect to some well-recorded historical events and considering the response of multiple degrees of freedom (MDoF) systems. Herein, validation encompasses detailed assessment of how similar is, for a given event, the seismic response due to comparable hybrid broadband simulated records and real records. In the first part of this study, in order to investigate the dynamic response of a wide range of buildings, MDoF structures are modeled as elastic continuum systems consisting of a combination of a flexural cantilever beam coupled with a shear cantilever beam. A number of such continuum systems are selected including the following: (1) 16 oscillation periods between 0.1 and 6 s; (2) three shear to flexural deformation ratios to represent respectively shear-wall structures, dual systems, and moment-resisting frames; and (3) two stiffness distributions along the height of the systems, that is, uniform and linear. Demand spectra in terms of generalized maximum interstory drift ratio (IDR) and peak floor acceleration (PFA) are derived using simulations and actual recordings for four historical earthquakes, namely, the 1979 Mw 6.5 Imperial Valley earthquake, 1989 Mw 6.8 Loma Prieta earthquake, 1992 Mw 7.2 Landers earthquake, and 1994 Mw 6.7 Northridge earthquake. In the second part, for two nonlinear case study structures, the IDR and PFA distributions over the height and their statistics, are obtained and compared for both recorded and simulated time histories. These structures are steel moment frames designed for high seismic hazard, 20-story high-rise and 6-story low-rise buildings. The results from this study highlight the similarities and differences between simulated and real records in terms of median and intra-event standard deviation of logs of seismic demands for MDoF building systems. This general agreement, in a broad range of moderate and long periods, may provide confidence in the use of the simulation methodology for engineering applications, whereas the discrepancies, statistically significant only at short periods, may help in addressing improvements in generation of synthetic records. Copyright © 2013 John Wiley & Sons, Ltd.
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Structure-Specific Scalar Intensity Measures for Near-Source and Ordinary Earthquake Ground Motions
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Introduced in this paper are several alternative ground-motion intensity measures (IMs) that are intended for use in assessing the seismic performance of a structure at a site susceptible to near-source and/or ordinary ground motions. A comparison of such IMs is facilitated by defining the "efficiency" and "sufficiency" of an IM, both of which are criteria necessary for ensuring the accuracy of the structural performance assessment. The efficiency and sufficiency of each alternative IM, which are quantified via (i) nonlinear dynamic analyses of the structure under a suite of earthquake records and (ii) linear regression analysis, are demonstrated for the drift response of three different moderate- to long-period buildings subjected to suites of ordinary and of near-source earthquake records. One of the alternative IMs in particular is found to be relatively efficient and sufficient for the range of buildings considered and for both the near-source and ordinary ground motions.
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