Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanSTRONG GROUND MOTION FROM THE 2010 Mw 8.8
MAULE CHILE EARTHQUAKE AND ATTENUATIONRELATIONS FOR CHILEAN SUBDUCTION ZONEINTERFACE EARTHQUAKES
Rubén BOROSCHEK1 and Víctor CONTRERAS2
1

Associate Professor, Department of Civil Engineering, University of Chile,
Santiago, Chile, rborosch@ing.uchile.cl2
Research Assistant, Department of Civil Engineering, University of Chile,
Santiago, Chile, vicontre@ing.uchile.cl

ABSTRACT: The Mw 8.8 Maule Chile earthquake is one of the largest magnitude
events to have produced strong motion recordings world-wide. In this paper we describe
attributes of the recording stations, the data processing procedures and ground motion
intensity measures computed from the records. We then compare spectral accelerations topredictions from GMPEs. Finally we present preliminary attenuation relations forhorizontal spectral accelerations developed using a database of Chilean accelerograms
recorded during interface earthquakes occurred between 1985 and 2010.
Key Words: Maule Chile earthquake, strong ground motion, attenuation, subduction
zone, ground motion prediction

INTRODUCTION
The Mw 8.8 Chile earthquake occurred on February 27, 2010 in the south central Chilean region ofMaule. This earthquake is associated with the subduction process of the Nazca plate beneath the SouthAmerican plate, and it is one of the largest magnitude events to have produced strong motion
recordings world-wide. There were around 30 relevant strong motion recordings from currently
accessible arrays, over a rupture distance range of 30 to 700 km. These recordings come from the
University of Chile research arrays.
In this paper we describe attributes of the recording stations, the data processing procedures, andground motion intensity measures computed from the records. We then compare spectral accelerations
to predictions from GMPEs. Existing well known GMPE for interface subduction events captures well
the distance scaling and dispersion of the data, but under-predicts the overall ground motion level.
Finally we present attenuation formulas for horizontal Peak Ground Accelerations (PGA) andhorizontal Spectral Accelerations (SA) obtained using a database of Chilean seismic records. The
database used contains accelerograms recorded during interface earthquakes occurred between 1985
and 2010, including the accelerograms from the 2010 Mw 8.8 Maule Chile earthquake.

1722

STRONG GROUND MOTION FROM THE 2010 Mw 8.8 MAULE CHILE EARTHQUAKEThe University of Chile (UCh) has maintained strong motion arrays in operation since the mid-1960,
controlled by the National Accelerograph Network at the Department of Civil Engineering(RENADIC) and the Seismological Service at the Department of Geophysics (GUC). Most of the
instruments are analogue accelerometers (SMA-1 or similar) located inside one story buildings. The
Mw 8.8 Chile earthquake was recorded by the UCh strong motion arrays. Table 1 indicates location of
the recording stations, orientation of the instruments and geological and geotechnical conditions.
Data processing procedure
The procedure used in record processing is similar to techniques described in the literature for high-cut
filtering (Akkar et al. 2011) and for low-cut filtering (Akkar and Bommer 2006 and Paolucci et al.
2008). Recordings were digitized and processed in order to preserving high and low frequency signal
to the extent possible. The Fourier Amplitude Spectrum (FAS) was inspected in log-log space toidentify the maximum usable frequency (fmax) and to preliminarily estimate the low-cut filter corner(fmin). Typically, fmax was taken as 90 Hz for a Nyquist frequency of 100 Hz and 40 Hz for a Nyquist
frequency of 50 Hz. An iterative process was performed to select the final value of fmin, in which thevalue was varied up and down and the integrated displacement histories and displacement response
spectra were inspected. This process is illustrated in Fig. 1 for the VINA record. We seek the lowest
value of fmin that preserves a natural appearance to the record in the time domain without obvious drift
from low frequency noise. For the VINA record (NS component), fmin was selected as 0.03 Hz.
Filtering was applied in the time domain using an acausal fourth order Butterworth filter. Finally,
pseudo acceleration response spectra at 5% damping were calculated for a period band ending slightly
short of 1/fmin. More details about record processing can be found in Boroschek et al. 2012.

Fig. 1 Sensitivity of integrated displacements and displacement response spectra to different low-cut
filter corners. The case indicated with ‘NO’ corresponds to direct integration of the VINA record.
Ground motion intensity measures of selected recordings
Finite fault models of the earthquake rupture have been generated by USGS 2010 and Delouis et al.
2010 (DEA) based on different data sources. The rupture plane used for distance calculation istrimmed from the DEA fault plane to envelope the high-slip region (530x150 km).
The closest instruments to the fault plane are in Concepción city: CCSP (relatively firm soil) andCONC (relatively soft soil) with rupture distances of 34-35 km. In Fig. 2(a) we present geometricmean spectra of these records. The relatively firm soil conditions at CCSP produced large spectral
peaks above 2g at short periods (∼0.2 s), while the softer conditions at CONC produced much lower
short period spectral accelerations and a pronounced spectral peak from 1.5-2.2 s. The CONT station(soft soil) has much higher spectral ordinates over a broad period range (0.2 to 1.5 s), which may be asite effect that is much more broadly banded than that at CONC.

1723

1724

Code

Name

VS30b

Average shear-wave velocity over the top 30 m, in m/sec, based on the following references: [1] Arango et al., 2010; [2] Daza, 2003; [3] U. of Chile, 2012; [4] Kataoka, 2011; [5]Ortigosa, 2011. For calculation purposes, when VS data were available at depths <30 m, the VS value of the last layer was assumed constant to 30 m depth.

Data indicated with asterisk correspond to preliminary information, which are still under investigation.

*

Clay with lenses of sand & gravel[1]Continental sediments[2]*Granite[3]; Weathered rock[3]517[1]
Intrusive rock[2]Alluvial deposit[2]Alluvium & sand[3]; Sand[3]273[1]
Volcanic rock[3]; Rock[3]1421[1]
Silty sand with poorly graded gravel[4]280[2]
Fill[3]; Soil[3]; Artificial fill[3]360[1][5]
Poorly graded sand & clay
~340[3]
Gravel[6]Intrusive rock[6]Alluvium & gravel[7]Gravel[7]Clay & Gravel[5]~452[3]
Poorly graded gravel & pumicite[5]~450[3]
Gravel[8]~685[4][7]
GravelGravel & alluvium[8]Sandstone & volcanic rock[3]; Dense sand[3] 305[1]Gravel[9]Gravel[5]~705[3]
Sand[2]*~400[3][3][3]
Alluvium ; Dense Gravel527[1]
Alluvial deposit[2]~540[4]Silt[10]~340[3]
Alluvium[3]; Dense Gravel[3]~640[3][11]
Silty sand230[5]
Clay & gravel lying on metamorphic rock[5] ~395[3]Silt, clay & tuff[5]~325[3][2]
Silty clay *-Surface geologya

Geological and geotechnical information availableb

Orientation
Horizontal
ChannelsAzimuthNS EW V0
NS EW V0L
T V
60
NS EW V0
NS EW V0
NS EW V0L
T V
180
NS EW V
0
L
T V
310
L
T V
0
NS EW V0
NS EW V0
NS EW V
0L
T V
270
NS EW V0
NS EW V0
NS EW V0
NS EW V0
NS EW V
0L
T V
340
NS EW V
0
L
T V
0
L
T V
0
L
T V
0
NS EW V
150
L
T V
0
L
T V
0
L
T V
60
NS EW V0
NS EW V0
NS EW V0

Description of the surface geology based on the following references: [1] Ruz, 2011; [2] Geologic map of Chile SNGM, 2003; [3] Arango et al., 2010; [4] Daza, 2003; [5]University of Chile, 2012; [6] Siebert et al., 2005; [7] Leyton et al., 2010; [8] Ortigosa, 2011; [9] Álvarez, 2006; [10] Taiba, 2010; [11] Ramírez and Vivallos, 2009.

Location
Lat
Long
(S)
(W)
27.374 70.322
28.576 70.755
32.507 71.448
32.976 71.016
32.994 71.173
33.025 71.553
33.035 71.596
33.048 71.510
33.048 71.604
33.321 71.411
33.396 70.537
33.441 70.643
33.452 70.531
33.467 70.652
33.501 70.579
33.509 70.772
33.514 70.606
33.569 70.634
33.577 70.581
33.616 71.611
33.641 70.354
33.687 71.214
33.960 71.873
34.977 71.805
34.990 71.236
35.340 72.406
35.430 71.665
36.828 73.048
36.844 73.109
37.795 72.706
39.831 73.239

a

1
COPI COPIAPÓ-Hospital [RENADIC]
2 VALLE VALLENAR-Liceo Santa Marta [RENADIC]3
PAP PAPUDO [RENADIC]
4 ROBL CERRO EL ROBLE [GUC]
5 OLMU OLMUÉ-Casa Particular [GUC]
6 VINA VIÑA DEL MAR-Centro [RENADIC]
7 VALU VALPARAÍSO-UTFSM [RENADIC]8
MAR VIÑA DEL MAR-Puente Marga Marga [RENADIC]
9
VAL VALPARAÍSO-Almendral [RENADIC]
10 CASB CASABLANCA-Teatro Municipal [GUC]
11 LCON LAS CONDES-Cerro Calán [GUC]
12 SLUC SANTIAGO-Cerro Santa Lucía [GUC]
13 LRNA LA REINA-Colegio Las Américas [GUC]
14 SANT SANTIAGO-Conjunto Villa Andalucía [RENADIC]
15 HTIS PEÑALOLÉN-Hospital Luis Tisné [RENADIC]
16 CRMA MAIPÚ-Centro de Referencia de Salud [RENADIC]
17 MET LA FLORIDA-Metro Línea 5 Estación Mirador [RENADIC]
18 ANTU LA PINTANA-Antumapu [GUC]
19 HSOR PUENTE ALTO-Hospital Sótero del Río [RENADIC]
20
LLO LLOLLEO [RENADIC]
21 SNJM SAN JOSÉ DE MAIPO-Municipalidad [GUC]
22 MELP MELIPILLA-Compañía de Bomberos [GUC]
23 MAT MATANZAS-Escuela Carlos Ibáñez del Campo [RENADIC]
24 HUAL HUALAÑÉ-Hospital [RENADIC]
25 CURI CURICÓ-Hospital [RENADIC]
26 CONT CONSTITUCIÓN-Hospital [RENADIC]27
TAL TALCA-Colegio Integrado San Pío X [RENADIC]
28 CONC CONCEPCIÓN-Colegio Inmaculada Concepción [REN.]
29 CCSP CONCEPCIÓN-Colegio San Pedro de la Paz [GUC]
30 ANGO ANGOL-Hospital [RENADIC]
31 VALD VALDIVIA-Hospital [RENADIC]#

StationTable 1 Ground motion stations that recorded the 2010 Mw 8.8 Chile earthquake (adapted from Boroschek et al. 2012)

Fig. 2(b) shows geometric mean spectra of records with Rrup~50 km. LLO and HUAL stations arelocated around the north part of the fault and, despite the geographic distance between them (about
150 km), present similar spectral shapes. ANGO station, located around the south part of the fault,presents spectra with high accelerations for short periods and a large peak close to 3.5g at 0.2 s. Fig.
2(c) shows geometric mean spectra of seven records from the Santiago region. We observed similar
spectral shapes with spectral peaks over a period range of 0.15 to 0.5 s. An exception is the CRMA
station which presents higher short period spectral accelerations (by a factor of 2 compared with otherrecords) and a spectral peak of 2g at 0.5 s. Fig. 2(d) shows geometric mean spectra from the Valparaíso
and Viña del Mar region, where four stations are located very close to each other with rupture
distances from 95-99 km. Data is plotted for stations VALU (rock) and three soil stations VINA, MAR,and VAL (soft soil). Site amplification is evident at the soil sites with apparent site periods of 0.5-1.0 s.

Fig. 2 Geometric mean spectra of some representative records
In Table 2 we present, for the closest sites to the fault, the intensity measures of: PGA, PGV, PGD and
5% damped PSa at 0.1, 0.2, 1.0, 2.0 and 3.0 s for the two horizontal components of recordings. The
maximum PGA was 0.93g at station ANGO, the maximum PGV was 67 cm/s at station CONT and the
maximum PGD was 40 cm at station SLUC. We also include in Table 2 Arias Intensity, Significant
Duration (defined from the 5-95% time interval on a normalized Arias intensity plotted v/s time) andCentral Frequency (Vanmarcke 1976). There is a strong motion record at Cauquenes that was saturated
with a clip value of 1g. Additional studies are underway to derived reliable information.

Fig. 3 (a) 5-95% Significant Duration and (b) Arias Intensity versus rupture distance1725

5-95% significant durations ranged from about 30-90 s, although perceptible durations were oftenmuch longer at 2-3 min. Fig. 3(a) shows variation of significant durations (maximum value of the twohorizontal components is considered) with distance. It is observed a decreasing trend. Fig. 3(b) shows
variation of Arias intensity (calculated as the sum of the Arias intensity of the three components).
Table 2 Ground motion intensity measures (derived from Boroschek et al., 2012)
Code
Station(Rrup)CCSP(34 km)CONC(35 km)CONT(39 km)MAT(41 km)LLO(51 km)
HUAL(52 km)ANGO(54 km)MELP(65 km)TAL(66 km)CASB(78 km)CURI(85 km)VAL(95 km)VALU(96 km)MAR(98 km)VINA(99 km)CRMA(101 km)
SLUC(113 km)

Channel

PGA
(g)

PGV
(cm/s)

PGD
(cm)

NS
EW
L
T
L
T
L
T
L
T
L
T
NS
EW
L
T
L
T
L
T
NS
EW
L
T
L
T
NS
EW
NS
EW
NS
EW
NS
EW

0.65
0.61
0.40
0.28
0.55
0.63
0.34
0.30
0.32
0.57
0.39
0.46
0.93
0.68
0.57
0.77
0.48
0.42
0.29
0.33
0.47
0.41
0.22
0.27
0.14
0.31
0.35
0.34
0.22
0.33
0.56
0.48
0.24
0.34

38
44
67
50
44
67
42
28
26
31
39
36
29
40
24
42
28
34
33
27
31
37
29
22
7
16
39
46
24
35
47
39
25
44

16
15
21
16
11
16
9
7
4
5
5
7
23
34
6
12
4
7
7
17
19
29
5
4
2
3
18
12
24
21
15
24
39
40

5% damped PSa (g)0.1sec 0.2sec
1.38
2.15
0.91
1.79
0.61
1.05
0.39
0.67
0.70
1.68
0.93
1.83
0.41
0.85
0.42
0.77
0.85
1.08
1.03
1.82
1.03
1.06
1.29
0.96
1.73
3.23
1.49
2.37
1.11
1.90
1.29
1.60
0.77
1.22
1.01
1.79
0.37
0.56
0.49
0.71
1.39
1.46
1.08
1.11
0.28
0.45
0.33
0.66
0.35
0.30
0.60
0.72
0.61
0.79
0.52
0.80
0.31
0.49
0.58
0.60
0.61
0.96
0.70
0.84
0.39
0.94
0.44
0.47

1sec
0.49
0.81
0.39
0.35
0.57
1.14
0.72
0.41
0.32
0.66
0.53
0.49
0.21
0.46
0.17
0.60
0.31
0.38
0.28
0.51
0.43
0.41
0.68
0.49
0.13
0.15
0.75
1.12
0.50
0.46
0.38
0.48
0.20
0.63

2sec
0.15
0.30
1.13
0.51
0.34
0.25
0.35
0.18
0.08
0.11
0.12
0.12
0.09
0.16
0.09
0.11
0.13
0.19
0.06
0.07
0.16
0.17
0.10
0.08
0.04
0.07
0.09
0.17
0.08
0.07
0.12
0.23
0.15
0.23

3sec
0.08
0.08
0.18
0.14
0.13
0.17
0.15
0.09
0.05
0.06
0.07
0.10
0.03
0.07
0.07
0.09
0.05
0.08
0.03
0.04
0.09
0.07
0.04
0.04
0.04
0.04
0.04
0.06
0.04
0.06
0.07
0.11
0.06
0.14

Arias
Significant
Intensity
Duration
(m/s)
(sec)
69.7
17.31
73.8
14.26
80.6
8.79
87.9
5.72
59.8
19.85
65.2
26.28
34.0
7.10
35.0
4.55
36.2
5.00
32.0
10.26
61.7
7.91
56.0
8.71
50.8
19.93
49.8
17.54
31.9
8.99
31.8
12.69
69.9
11.61
71.9
11.06
32.2
3.68
30.1
3.80
50.2
10.71
51.7
11.06
31.4
2.30
27.3
2.04
25.0
0.28
21.9
0.50
30.5
4.45
33.6
4.73
29.4
2.07
24.6
3.84
32.1
5.77
33.8
4.93
40.7
2.80
37.8
2.80

Central
Freq.
(Hz)
4.04
4.16
2.13
2.54
2.97
2.82
2.29
2.89
4.36
4.16
4.81
5.03
4.86
4.76
6.96
5.97
5.14
5.14
2.89
2.97
5.57
4.68
1.92
2.44
5.13
4.62
3.01
3.03
2.26
1.85
2.60
2.84
4.96
3.64

Comparisons of spectral accelerations to predictions from GMPEs
We briefly compare in this section spectral accelerations to estimations from ground motion prediction
equations (GMPEs), examining primarily the ground motion level and the distance attenuation of theMaule data. Relatively recent GMPEs for interface subduction zone earthquakes were developed by
Atkinson and Boore 2003, 2008 and Zhao et al. 2006, which we referred to subsequently as AB03 and
ZEA06. The AB03 interface model was derived exclusively from subduction zone interface
earthquakes. In contrast, the ZEA06 model constrains near fault ground motions from crustal and slab
earthquakes. Fig. 4 shows geometric mean PGA, 0.2 s, 1.0 s and 2.0 s pseudo spectral accelerations(PSa) at 5% damping versus rupture distance. Also shown in Fig. 4 are medians for the AB03 and
ZEA06 GMPEs, plotted for the C/D boundary by averaging predictions for the two site classes.

1726

It is observed that the variation of Maule data with distance is consistent with the AB03 GMPE, which
was developed specifically for interface subduction earthquakes, but the Maule data areunder-predicted by the AB03. The ZEA06 GMPE has significantly faster distance attenuation rates
than the AB03 model and over-predicts the attenuation rate of the Maule data.

Fig. 4 Attenuation of PGA and spectral accelerations with distance and comparison to GMPEs

ATTENUATION RELATIONS FOR CHILEAN INTERFACE EARTHQUAKESWe present attenuation formulas for horizontal Peak Ground Accelerations (PGA) and horizontal
Spectral Accelerations (SA) developed using a database of Chilean seismic records. Attenuation
curves were estimated using the maximum likelihood regression method. The proposed formulas take
into account differences in the soil type according to the Chilean code soil classification.
Strong Motion Database
The database used contains accelerograms recorded in Chilean territory during interface(thrust-faulting) earthquakes occurred between 1985 and 2010, including the accelerograms from the2010 Mw 8.8 Maule Chile earthquake. The database was generated from public accelerographic data
and accelerograms recorded by the UCh through the RENADIC and the Seismological Service (GUC).
We used a subset of the overall database compiled considering only the interface events withmagnitude Mw ≥ 6.5. The resulting subset consists in 117 accelerograms from 13 interface
earthquakes recorded at 79 stations, located at distances between 30 and 600 km.
The earthquakes used in this study, listed in Table 3, correspond to 9 main events and 4 aftershocks
with large magnitudes. Moment magnitude (Mw) was used, which was obtained from a search of theHarvard Centroid Moment Tensor (CMT). The date, time, location of the epicenters (Lat, Long) andfocal depth (H) were taken from the Seismologic Service of the UCh. The epicenters of earthquakes
and location of the recording stations are shown in Fig. 5 (in this Figure the earthquakes are listed asindicated in Table 3). Despite the small dataset, this is an initial attempt to capture the general behavior
of GMPE at different SA periods for the country.
Due to the limited number of accelerograms used in this study, we decided to classify the sites of
the recording stations only into two generic groups: Rock and Soil. Based on different type ofgeotechnical information we classify the sites according to the Chilean code soil classification,
considering that the sites located on Rock comply with VS30 ≥ 900 m/s (average shear wave velocity

1727

over 30 m), or RQD ≥ 50% (Rock Quality Designation according to ASTM D 6032), or qu ≥ 10 MPa(Compressive Strength). In other cases we classify the sites as Soil.
Table 3 List of interface earthquakes used to develop attenuation relations
Number of Records
Date
UTC Time
Lat.
Long.
H
Mw
(dd-mm-yy)(hh:mm)
S
W
(km)
Rock
Soil
1
03-03-1985
22:46
7.9
-33.24-71.8533
522
203-03-1985(a)
23:38
7.3
-32.74-71.21
33
1
2
01:56
7.1
-34.13-71.6238
1
9
3
09-04-1985(a)430-07-1995
05:11
8.0
-23.57-70.6033
11
530-01-1998
12:16
7.0
-23.51-69.8344
10
6
23-06-2001
20:33
8.4
-16.26-73.6433
1
6
7
07-07-2001(b)
09:38
7.6
-17.40-71.8037
01
818-04-2002
16:08
6.6
-27.51-70.0953
10
920-06-2003
13:30
6.8
-30.65-71.8124
0
1
10 30-04-2006
21:40
6.5
-26.84-71.1518
0
2
11 14-11-2007
15:40
7.7
-22.69-70.22
39
6
11
08:09
6.7
-22.95-70.18425
912 16-12-2007(c)13 27-02-2010
06:34
8.8
-36.29-73.2430
328(a) Aftershocks of the 03-03-1985 (22:46) earthquake. (b) Aftershock of the 23-06-2001 earthquake.
(c) Aftershock of the 14-11-2007 earthquake.
#

Focal mechanisms were obtained from published works and from the CMT solutions. This
information was subsequently revised considering the proximity of the events to the subduction zone
interface and the alignment of the mechanisms with the dip of the interface. The closest distance to therupture surface (Rrup) is used as source to site distance. To estimate this parameter we modeled theearthquakes fault plane using the CMT solutions and the aftershocks distributions. For main events
without a defined aftershock rupture area (events 5 and 8) and for aftershocks of the 03-03-1985
earthquake (events 2 and 3) we used hypocentral distance instead of Rrup. The magnitude-distance
distribution of the database used is shown in the Fig. 6.

Fig. 5 Map of north and central Chile showing epicenters (listed circles) of earthquakes used in thisstudy. Red circles correspond to main events and orange circles correspond to aftershocks. The circles
size is proportional to the magnitudes. Grey triangles represent the strong motion stations.

1728

Fig. 6 Distribution of the data for interface earthquakes used in this study
Regression method and functional form
Regression of the database was performed using the one-stage maximum likelihood regression method.
We used the following simple functional form:

log10 (Y ) = C1 + C2 M w + C3 H + C4 R − g log10 ( R ) + C5 Z

(1)where Y is either Peak Ground Acceleration (PGA) or 5% damped Spectral Acceleration (SA). In
both cases the geometric mean of two horizontal components in units of g was used. M W is themoment magnitude, H is the focal depth in kilometers, R =Rrup 2 + Δ 2 with

Rrup the closest

distance to the rupture surface in kilometers and Δ a near-source saturation term, given by
Δ = C610C7 M w . g = C8 + C9 M w is the geometrical spreading coefficient. For Rock sites Z = 0 and
for Soil sites Z = 1 . Coefficients Ci , with i = 1,...,9 , were determined by regression analysis.
The coefficients C6 and C7 (associated to the near-source saturation term) and the coefficients C8
and C9 (associated to the geometrical spreading coefficient) were calculated using an optimization
algorithm that allowed minimize the mean of residuals for the PGA data with distances lesser than orequal to 80 km. This subset of the data, consisting in 47 recordings, was selected considering the
distance range where the possible saturation occurs. These coefficients were fixed for all periods
analyzed. The coefficients C1, C2, C3, C4 and C5 were calculated using the one-stage maximum
likelihood regression method for each period; therefore the values of these coefficients vary with theperiod.
Results of the regression
The regression coefficients obtained for all the periods analyzed are shown in the Table 4. As found inprevious work, there is a weak depth effect given by the coefficient C3, with deeper events causinglarger accelerations. Inspection of the coefficients C5 shows that Soil accelerations exceed Rockaccelerations by a factor ranging from 1.6 to 2. Standard deviations of the residuals (σ) are in therange of 0.21 to 0.26. Fig. 7 shows 0.04 and 1.0 s predicted spectral accelerations versus rupture
distance for different magnitudes and soil conditions. It is clearly observed the effect of the saturation
term for large magnitudes and near to fault distances. In Fig. 8 we compare predicted and observed
accelerations for PGA, 0.4, 1.0 and 2.0 s, considering an earthquake with Mw=8.8 and H=30 km.
Predicted curves proposed in this study for Rock and Soil are plotted. Also AB03 and ZEA06 models
are plotted for the C/D boundary by averaging predictions for the two site classes.

1729

1
0.5

1
0.5

0.04 s0.1
0.05
SA (g)SA (g)

0.1
0.05
0.01
0.005

0.01
0.005

M =6.5Rockw
M =8.5 H= 30 kmw
M =7.50.001

M =6.5w

w

0.001

M =7.5w

M =8.5
w

1s

0.5

Soil
H= 30 km

1s

0.5
0.1
0.05
SA (g)0.1
0.05
SA (g)

0.04 s

0.01
0.005

0.01
0.005
M =6.5

M =6.5

w

w

0.001

Rock
M =8.5 H= 30 km
w

0.001

M =7.5
w

20

30

50

100

M =7.5w

M =8.5w

200

Soil
H= 30 km

20 30
50
100
200
400 600
Closest distance to the rupture surface, Rrup (km400 600

Closest distance to the rupture surface, Rrup (km)Fig. 7 Attenuation curves obtained plotted for different magnitudes
1

3
2

PGA

0.4 s

0.5
1

SA (g)PGA (g)

0.5
0.1
0.05

0.01

1

Rock-This study
Soil-This study
AB03
ZEA06
Mw=8.8±0.5 ε = 0.01
Rock
Soil
H=30 kmσ = 0.191

0.1
0.05

1

1s

Rock-This study
Soil-This study
AB03
ZEA06
Mw=8.8±0.5 ε = -0.001
Rock
Soil
H=30 kmσ = 0.207

2s

0.5

0.1

SA (g)SA (g)

0.5

0.1
0.05

Rock-This study
Soil-This study
AB03
ZEA06
Mw=8.8±0.5 ε = 0.007
Rock
Soil
H=30 kmσ = 0.205

0.05

0.01
0.005

20 30
50
100
200
400 600
Closest distance to the rupture surface, Rrup (km)Rock-This study
Soil-This study
AB03
ZEA06
Mw=8.8±0.5 ε = 0.024
Rock
Soil
H=30 kmσ = 0.248

20 30
50
100
200
400 600
Closest distance to the rupture surface, Rrup (km)Fig. 8 Comparison between predicted and observed accelerations (Mw=8.8±0.5, H=30 km). The meanof residuals (ε) and the standard deviation of residuals (σ) for the data shown are indicated.

1730

It is observed that the relations obtained present a good fit for the earthquake data plotted(Mw=8.8±0.5). AB03 GMPE under-predicts the acceleration level, but it is consistent with thevariation of data with distance (excepting 2.0 s data). The ZEA06 GMPE over-predicts the attenuationrate.
EQ: 03-Mar-1985 Mw=7.9 H=33 km
TALCA - COLEGIO INTEGRADO SAN PÍO X (Soil) Rrup=120.3 km

EQ: 14-Nov-2007 Mw=7.7 H=38.9 km
ALTO HOSPICIO - MUNICIPALIDAD (Soil) Rrup=175.6 km
Horizontal components
Data used (geometric mean)
Soil-This study
Soil - Y(1997)
NEHRP C - A&B(2003)
Site Class II - Z(2006)

0.4
0.35

0.5

0.25

SA (g)SA (g)

0.3

Horizontal components
Data used (geometric mean)
Soil-This study
Soil - Y(1997)
NEHRP C - A&B(2003)
Site Class II - Z(2006)

0.6

0.2

0.4

0.3

0.15

0.2
0.1

0.1

0.05
0
0

0.5

1

1.5

0
0

2

0.5

1

1.5

Period, T (s)Period, T (s)EQ: 03-Mar-1985 Mw=7.9 H=33 km
VALPARAISO - UTFSM (Rock) Rrup=38 km

EQ: 14-Nov-2007 Mw=7.7 H=38.9 km
PUERTO PATACHE (Rock) Rrup=118.5 km

Horizontal components
Data used (geometric mean)Rock - This study
Rock - Y(1997)
NEHRP B - A&B(2003)
Site Class I - Z(2006)

0.6

0.5

2

Horizontal components
Data used (geometric mean)Rock - This study
Rock - Y(1997)
NEHRP B - A&B(2003)
Site Class I - Z(2006)

0.25

0.2

SA (g)SA (g)

0.4

0.3

0.15

0.1
0.2
0.05

0.1

0
0

0.5

1

1.5

0

2

0

0.5

Period, T (s)EQ: 27-Feb-2010 Mw=8.8 H=30 km
CONCEPCION - COLEGIO SAN PEDRO DE LA PAZ (Soil) Rrup=34 km

2

1.5

Horizontal components
Data used (geometric mean)
Soil-This study
Soil - Y(1997)
NEHRP C - A&B(2003)
Site Class II - Z(2006)

1

SA (g)SA (g)

1.5

1.5

EQ: 27-Feb-2010 Mw=8.8 H=30 kmVIÑA DEL MAR - CENTRO (Soil) Rrup=99 km

Horizontal components
Data used (geometric mean)
Soil-This study
Soil - Y(1997)
NEHRP C - A&B(2003)
Site Class II - Z(2006)

2

1

Period, T (s)

1

0.5
0.5

0

0

0.5

1

1.5

2

Period, T (s)

0

0

0.5

1

1.5

Period, T (s)Fig. 9 Comparison of observed response spectra versus predicted response spectra

1731

2

Fig. 9 shows a comparison of observed response spectra versus predicted response spectra for some
representative records. The relations proposed in this study, generally result in higher accelerations
than those estimated in other works, excepting the case of ZEA06 model for near to fault distances.
Table 4 Regression coefficients
Period
(sec)
PGA
0.04
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
2.00

C1

C2

C3

C4

C5

C6

C7

C8

C9

σ

-1.8559-1.7342-1.4240-1.0028-1.2836-1.4161-2.1228-2.7134-2.9001-3.0909-3.1439-3.3352-3.5092-3.5599-3.6365-3.7061-3.7750-3.90510.25490.25670.25970.23750.25190.25680.32080.36680.37950.40050.39520.40130.40930.40790.40900.4096
0.40890.40790.01110.01110.00810.00230.00440.00490.00940.01410.01520.01470.01630.01860.02020.0211
0.02180.02250.02280.0215-0.0013-0.0016-0.0019-0.0014-0.0009-0.0008-0.0008-0.0008-0.0009-0.0009-0.0010-0.0010-0.0011-0.0011-0.0010-0.0010-0.0010-0.00080.30610.28650.2766
0.26990.29770.31500.28340.2824
0.29690.28340.27300.28390.28490.27000.26310.25550.25280.20570.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.07340.35520.35520.35520.35520.35520.35520.35520.35520.35520.35520.35520.35520.35520.35520.35520.35520.35520.3552

1.51491.51491.51491.51491.51491.51491.51491.51491.51491.51491.51491.51491.51491.51491.51491.51491.51491.5149-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.103-0.1030.21370.23110.25570.24690.24340.24140.22720.21740.22210.22790.22600.2351
0.23790.23740.24290.24250.24590.2592

CONCLUSIONSThe 2010 Mw 8.8 Maule Chile earthquake produced about 30 relevant strong motion recordings over a
rupture distance range of 30 to 700 km. The strong motion data were processed using high- andlow-cut filters designed to optimize the usable frequency range. Ground motion intensity measures
were presented, including PGA, PGV, PGD, 5% damped pseudo spectral accelerations, 5-95%
significant duration, Arias intensity and Central frequency. Significant durations for this earthquake
generally ranged from about 30 to 90 s. Data from the Concepción and Viña del Mar areas exhibit site
effects with respective site periods of about 1.5-2.2 s and 0.5-1.0 s. The variation of Maule data with
distance is consistent with the AB03 GMPE, but the Maule data are under-predicted by the AB03
model. The ZEA06 GMPE over-predicts the attenuation rate of the Maule data.
Accelerograms database was generated from public accelerographic data and data recorded by the
University of Chile. The earthquake database analyzed enabled a gross estimation of attenuation
relations for Chilean interface earthquakes. These GMPEs could be useful to improve the seismic
hazard assessment in Chile and others similar subduction zones. In particular, the relations obtained
present a good fit for earthquakes with larger magnitudes, and the logarithmic standard deviations of
the errors are in the range 0.21 to 0.26. The obtained curves indicate that the accelerations at stations
located in Soil are higher than those estimated at stations located on Rock by a factor of up to 2. For
the Chilean case, the horizontal accelerations are generally higher than those estimated in studies
where records from different subduction zones around the world are mixed. This issue highlights theneed to develop GMPEs for specific subduction zones.

ACKNOWLEDGMENTS
The financial and technical support of the Civil Engineering Department of University of Chile andthe effort of Eng. Pedro Soto installing and maintaining the instruments are gratefully acknowledged.

1732

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