EARTHQUAKES
2.1 INTRODUCTION
2.3.3 P ROPOSED M ETHODOLOGY FOR S ELECTING R EPRESENTATIVE E ARTHQUAKE S UITES
Based on the previous selection of the far- and near-fields, the procedure can be
summarised into steps that would be followed endeavouring a credible selection of
representative earthquake suites and scenarios. The steps are as follows:
1. Identify the level of PGA and Sa(T1) for the considered structure at the elected
percentage of damping, e.g. 5-percent.
2. From local faulting and seismology, and also informed by the governing loading code,
[NZS1170.5 (2004)] and seismic hazard maps identify whether near-, medium- and/or
far-field seismic events would be the representative scenario for the site of the
considered structure.
3. Obtain or calculate k0 and k seismic hazard coefficients of the site of the considered
structure in order to identify representative earthquakes from geographic area that
matches the considered seismic hazard.
4. Set the initial search parameters of the elected strong motion database, e.g. PEER
(2000), by moment magnitude (M) > 6.5 and closest distance to the rapture surface (R)
to be: R ≤ 8km, 8km ≤ R ≤ 40km and R ≥ 40km for near-, medium- and far-field events respectively. Also enforce damped PGA ≥ 0.2g and ≥ 0.4 for far- and near-field events respectively. Further, select representative soil classification albeit for credible
earthquake scenario it is preferable to choose at least C for USGS, D for Geomatrix or 1
for CWB classifications. Consequently, site-specific soil amplifications can be avoided.
5. Download the above-mentioned criteria-matched earthquakes including all their
component accelerograms and spectral accelerations, if available, else compute them.
7. Build an information table listing the properties of all components for each initially
selected earthquake. These data include accelerogram information including recording
station, component type and direction, M, R, damped PGA and Sa(T1) values.
8. Select earthquakes, including their components, that at least one of their horizontal
components has high value of Sa(T1). Consequently, limit the number of selected
earthquakes to a little more than 20, say about 25, that achieve the highest available
values of Sa(T1).
9. For far-field suites, plot spectral accelerations of the horizontal components between
the maximum and minimum spectral acceleration bounding values obtained from the
above-developed far-field suite. Subsequently, cull earthquakes that exceed 1/T or
have a component significantly exceeding the maximum bound in order to remove
earthquakes that breach the guidelines.
10. For near-field events, plotting spectral accelerations of the horizontal components
between the maximum and minimum spectral acceleration bounding values of the
above-developed near-field may be helpful. It would show whether the newly selected
near-field suite is relatively of lower or higher magnitude in comparison with the
above-developed one.
11. Scale and plot the spectral accelerations of the remaining horizontal components by
setting the value of PGA = 1g. Subsequently inspect the plot and eliminate any
earthquake with peculiar large peak values around a specific period value, as
highlighted previously in the case of Mexico City (1985) records, see Figure 2-2.
12. Moreover, scale and plot the remaining spectral accelerations by setting the values of
Sa(½T1) and Sa(T1) to 1g. Afterwards, inspect the plots for any peculiarities or marked
exceedance of the maximum bounding values in order to remove breaching
earthquakes. Note that scaling with the spectral acceleration values of one-third or
13. If the total number of earthquakes drops below 20, repeat the above detailed procedure
with slightly reduced thresholds of M, R and PGA. Repeat this procedure until 20
earthquakes are acquired. For near-field events, it is expected to later relax the rule of
selecting earthquakes only from geographic areas with matching seismic hazard due to
the scarcity of these records.
Note that for two-dimensional analysis, the same proposed procedure applies where both
horizontal accelerogram can be used along with the vertical one if considered. Consequently,
this methodology can be applied to both two- or three-dimensional studies of structures.
2.4 CONCLUSIONS AND RECOMMENDATIONS
The employed methodology in selecting both the far- and near-field proved credibility by
their reported reduced randomness (βEQ). Chapters four, five and six later show that marked reduced
randomness in the structural response and behaviour that assures the credibility of their findings. The
proposed stepwise procedure is portable and can be easily followed in selecting representative one-,
two- or three-dimensional earthquake suites and scenarios. Finally, it is worthwhile to mention that
South Californian strong motion records can be implemented in New Zealand, and vice versa, due to
the confirmed large resemblance in their seismic hazard characteristics.
It is highly recommended to follow the proposed procedure in selecting and/or verifying
the selection appropriateness of representative earthquake suites and scenarios. Earthquakes
recorded on soft soils should be strictly avoided to avoid site-specific amplification as depicted
in the case of the earthquake records of Mexico City (1985), see Figure 2-2.
2.5 REFERENCES
Abrahamson, N. A., and Silva, W. J. (1997). “Empirical response spectra attenuation relations for
shallow crustal earthquakes”, Seismological Research Letters (SRL), Vol. 68, pp94-127.
Federal Emergency Management Agency (FEMA) (2002). “Seismic rehabilitation pre-standard.”
DOE (1994). “Natural phenomena hazards design and evaluation criteria for Department of
Energy Facilities”, DOE-STD-1020-94, U. S. Dept. of Energy, Washington DC.
Federal Emergency Management Agency (FEMA) (2000). “FEMA 350 – Recommended
Seismic Design Criteria for New Steel Moment-Frame Buildings.” Report No. FEMA-
350, Washington DC.
Han, S.W., and Wen, Y.K. (1997). “Method of Reliability-Based Seismic Design. I: Equivalent
Nonlinear Systems. II: Calibration of Code Parameters”, Journal of Structural
Engineering, ASCE, Vol. 123. No. 3, pp. 256-270.
Kircher, C. A., Nassar, A. A., Kustu, O. and Holmes, W. T. (1997). "Development of Building
Damage Functions for Earthquake Loss Estimation", Earthquake Spectra, Vol. 13, No. 4,
pp. 663-682, Earthquake Engineering Research Institute, Oakland, California.
Luco, N., and, Cornell, C. A., (1998A). “Seismic drift demands for two SMRF structures with
brittle connections”, Structural Engineering World Wide 1998, Elsevier Science Ltd.,
Oxford, England, Paper T158-3.
NZS1170.5 and Supp 1 (2004). “Structural design actions – Earthquake actions – New Zealand”,
Standards New Zealand, 2 parts, Wellington, New Zealand.
PEER Strong Motion Database (2000). Complied by Dr. Walt Silva of Pacific Engineering,
Pacific Earthquake Engineering Research Center (PEER), University of California at
Berkeley. http://peer.berkeley.edu/smcat/.
Penzien, J. and Watabe, M. (1975). “Characteristics of 3-dimensional earthquake ground
motions”, Earthquake Engineering and Structural Dynamics, Vol. 3, pp. 365-373.
Shome, N., and Cornell, C. A. (1999). “Probabilistic seismic demand analysis of nonlinear
structures”, Report No. RMS-35, RMS Program, Stanford University, Stanford, CA.
http://www.stanford.edu/group/rms/Thesis/NileshShome.pdf. (Last time accessed: 08
January 2007).
motion time histories for phase 2 of the FEMA/SAC steel project.” SAC Background
Document SAC/BD-97/04, SAC Joint Venture, Richmond, California.
Stirling, M. W., McVerry, G. H. and Berryman, K. R. (2002). “A New Seismic Hazard Model
for New Zealand”, Bulletin of the Seismological Society of America, Vol. 92. No. 5, June
2002, pp. 1878-1903.
USGS (2002). “USGS national seismic hazard maps”, United States Geological Survey
http://geohazards.cr.usgs.gov/eq/.
Vamvatsikos, D., and Cornell C. A. (2002). “Incremental Dynamic Analysis”, Earthquake
Engineering and Structural Dynamics, Vol. 31, pp. 491–514.
Vamvatsikos, D., and Cornell, C. A. (2004). “Applied incremental dynamic analysis”,
Earthquake Spectra, Earthquake Engineering Research Institute (EERI), Vol. 20, No. 2,
Table 2-1. The Initial Earthquake Suite. EQ
No.
Suite
No. Event Station φ
(1) Soil(2)
M(3) R(km)(4) PGA(g)
1 1 Imperial Valley, 1940 El Centro 90 C,D 7 8.3 0.214
2 Imperial Valley, 1940 El Centro 0 C,D 7 8.3 0.348
2 3 Imperial Valley, 1979 Imperial County Services Bldg 90 ? 6.5 ? 0.236
4 Imperial Valley, 1979 Imperial County Services Bldg 0 ? 6.5 ? 0.213
3 5 Kobe, 1995 Kobe JMA Observatory 90 ? 6.9 19.163 0.631
6 Kobe, 1995 Kobe JMA Observatory 0 ? 6.9 19.163 0.837
4 7 Mexico City, 1985 CDAO, D3-115 0 D,E 8.1 400 0.071
8 Mexico City, 1985 CDAO, D3-115 90 D,E 8.1 400 0.082
5 9 Mexico City, 1985 SCT1, D3-144 0 D,E 8.1 400 0.100
10 Mexico City, 1985 SCT1, D3-144 90 D,E 8.1 400 0.171
6 11 San Fernando, 1971 Pacoima Dam 164 –,B 6.6 8 1.221
12 San Fernando, 1971 Pacoima Dam 254 –,B 6.6 8 1.246
7 13 Parkfield, 1966 Temblor 295 ? 6.1 61 0.281
14 Parkfield, 1966 Temblor 205 ? 6.1 61 0.410
8 15 Northridge, 1994 Pacoima Dam - Upper Left Abutment 194 A,A 6.6 18.573 1.284
16 Northridge, 1994 Pacoima Dam - Upper Left Abutment 104 A,A 6.6 18.573 1.584
9 17 Northridge, 1994 Sylmar-6 Storey C. Hosp., Ground, E. Wall 0 C,– 6.6 15.057 0.799
18 Northridge, 1994 Sylmar-6 Storey C. Hosp., Ground, S. Wall 90 C,– 6.6 15.057 0.383
10 19 Loma Prieta, 1989 Corralitos - Eureka Canyon Road 90 B,– 7 7.167 0.478
20 Loma Prieta, 1989 Corralitos - Eureka Canyon Road 0 B,– 7 7.167 0.630
11 21 Loma Prieta, 1989 Treasure Island 90 Fill 7 67.700 0.159
22 Loma Prieta, 1989 Treasure Island 0 Fill 7 67.700 0.100
(1)
Component.
(2)
USGS, Geomatrix soil class.
(3)
Moment magnitude.
(4)
Table 2-2. Linear regression coefficients (k0 and k) of Seismic hazard on intensity measure (Sa) for
Christchurch and Wellington, based on Stirling et al (2002).
Linear regression coefficients (k0 and k) of New Zealand
Seismic Hazard Wellington Christchurch PGA T=2s PGA T=2s k0 3 x 10-4 5 x 10-5 5 x 10-5 8 x 10-7 Median k0 0.0001 k -2.74 -2.43 -2.81 -3.58 Median k -2.78
Table 2-3. Sorted Vamvatsikos and Cornell (V&C) Far-Field Suite (May 2004). EQ
No.
Suite
No. (1) Event Station φ
(2) Soil(3)
M(4) R(km)(5) PGA(g)
1 13 Imperial Valley, 1979 Chihuahua 282 C,D 6.5 28.7 0.254
2 8 Imperial Valley, 1979 El Centro Array #13 140 C,D 6.5 21.9 0.117
14 Imperial Valley, 1979 El Centro Array #13 230 C,D 6.5 21.9 0.139
3 2 Imperial Valley, 1979 Plaster City 135 C,D 6.5 31.7 0.057
18 Imperial Valley, 1979 Plaster City 45 C,D 6.5 31.7 0.042
4 9 Imperial Valley, 1979 Westmoreland Fire Station 90 C,D 6.5 15.1 0.074
15 Imperial Valley, 1979 Westmoreland Fire Station 180 C,D 6.5 15.1 0.11
5 1 Loma Prieta, 1989 Agnews State Hospital 90 C,D 6.9 28.2 0.159
6 4 Loma Prieta, 1989 Anderson Dam Downstream 270 B,D 6.9 21.4 0.244
7 5 Loma Prieta, 1989 Coyote Lake Dam Downstream 285 B,D 6.9 22.3 0.179
8 19 Loma Prieta, 1989 Hollister Diff. Array 165 –,D 6.9 25.8 0.269
3 Loma Prieta, 1989 Hollister Diff. Array 255 –,D 6.9 25.8 0.279
9 10 Loma Prieta, 1989 Hollister South & Pine 0 –,D 6.9 28.8 0.371
10 7 Loma Prieta, 1989 Sunnyvale Colton Ave 270 C,D 6.9 28.8 0.207
11 Loma Prieta, 1989 Sunnyvale Colton Ave 360 C,D 6.9 28.8 0.209
11 16 Loma Prieta, 1989 WAHO 0 –,D 6.9 16.9 0.37
20 Loma Prieta, 1989 WAHO 90 –,D 6.9 16.9 0.638
12 12 Superstition Hills, 1987 Wildlife Liquefaction Array 90 C,D 6.7 24.4 0.18
17 Superstition Hills, 1987 Wildlife Liquefaction Array 360 C,D 6.7 24.4 0.2
13 6 Imperial Valley, 1979 Cucapah 85 C,D 6.5 23.6 0.309
(1)
The component’s original number V&C suite.
(2)
Component.
(3)
USGS, Geomatrix soil class.
(4)
Moment magnitude.
(5)
Closest distance to fault rupture.
Table 2-4. Statistical properties of the V&C Far-Field Suite. Criterion M(3) R(km)(4) PGA(g)
Max 6.9 31.7 0.638
Min 6.5 15.1 0.042
Std Deviation 0.189 5.059 0.133
Table 2-5. The Far-Field Suite: The Populated V&C Far-Field Suite, plus the Added 8 Far-Field Earthquakes.
EQ No.
Suite
No. (1) Event Station φ
(2) Soil(3)
M(4) R(km)(5) PGA(g)
1 13-b Imperial Valley, 1979 Chihuahua 12 C,D 6.5 28.7 0.27
13 Imperial Valley, 1979 Chihuahua 282 C,D 6.5 28.7 0.254
2 8 Imperial Valley, 1979 El Centro Array #13 140 C,D 6.5 21.9 0.117
14 Imperial Valley, 1979 El Centro Array #13 230 C,D 6.5 21.9 0.139
3 2 Imperial Valley, 1979 Plaster City 135 C,D 6.5 31.7 0.057
18 Imperial Valley, 1979 Plaster City 45 C,D 6.5 31.7 0.042
4 9 Imperial Valley, 1979 Westmoreland Fire Station 90 C,D 6.5 15.1 0.074
15 Imperial Valley, 1979 Westmoreland Fire Station 180 C,D 6.5 15.1 0.11
5 1-b Loma Prieta, 1989 Agnews State Hospital 0 C,D 6.9 28.2 0.172
1 Loma Prieta, 1989 Agnews State Hospital 90 C,D 6.9 28.2 0.159
6 4-b Loma Prieta, 1989 Anderson Dam Downstream 270 B,D 6.9 21.4 0.244
4 Loma Prieta, 1989 Anderson Dam Downstream 360 B,D 6.9 21.4 0.24
7 5-b Loma Prieta, 1989 Coyote Lake Dam Downstream 195 B,D 6.9 22.3 0.16
5 Loma Prieta, 1989 Coyote Lake Dam Downstream 285 B,D 6.9 22.3 0.179
8 19 Loma Prieta, 1989 Hollister Diff. Array 165 –,D 6.9 25.8 0.269
3 Loma Prieta, 1989 Hollister Diff. Array 255 –,D 6.9 25.8 0.279
9 10 Loma Prieta, 1989 Hollister South & Pine 0 –,D 6.9 28.8 0.371
10-b Loma Prieta, 1989 Hollister South & Pine 90 –,D 6.9 28.8 0.177
10 7 Loma Prieta, 1989 Sunnyvale Colton Ave 270 C,D 6.9 28.8 0.207
11 Loma Prieta, 1989 Sunnyvale Colton Ave 360 C,D 6.9 28.8 0.209
11 16 Loma Prieta, 1989 WAHO 0 –,D 6.9 16.9 0.37
20 Loma Prieta, 1989 WAHO 90 –,D 6.9 16.9 0.638
12 12 Superstition Hills, 1987 Wildlife Liquefaction Array 90 C,D 6.7 24.4 0.18
17 Superstition Hills, 1987 Wildlife Liquefaction Array 360 C,D 6.7 24.4 0.2