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This is an open-access database that archives thousands of papers published under the Auspices of the ISSMGE and maintained by the Innovation and Development Committee of ISSMGE. An Updated Probabilistic Seismic Hazard Assessment for Mexico City

Jongwon Lee, Pawan Kumar & Ibrahim Almufti Arup, San Francisco, CA, USA Manuela Villani Arup, London, UK

ABSTRACT This study presents a probabilistic seismic hazard assessment (PSHA) carried out for a confidential high-profile project in Mexico City. The seismic hazard is calculated for the “rock” level, where the rock corresponds to a shear wave velocity of approximately 600 m/s. The objective of this study is to develop rock input motions to carry out site-specific seismic soil response analyses for performance-based design. An up-to-date earthquake catalogue was developed for the study, which was collated from multiple reliable databases, and processed uniformly. Based on the earthquake catalogue and recent publications, seismic source zones were developed along with their estimated earthquake recurrence rates, maximum magnitudes, and hypocentral depth distributions. The major source of earthquake hazard to Mexico City is the subduction zone of the Pacific Ocean, where the Cocos plate subducts beneath the North America plate, for which interface and intraslab plates were separately modelled as subduction source zones. The Trans-Mexican Volcanic Belt (TMVB) is also modelled even though it has relatively low seismicity. This study also evaluated the suitability of multiple ground motion prediction equations (GMPEs) in predicting the spectral shape and amplitude expected from distant subduction earthquakes against local measurements from past seismic events. It concluded that the global GMPEs were inappropriate because of the unique characteristics of subduction ground motions observed in the Mexico City area. Consequently, local subduction GMPEs were employed for the PSHA, but with the magnitude-scaling term adjusted for very large magnitudes (MW > ~8.1) due to the lack of local large-magnitude data. The PSHA results show that the subduction sources contribute predominantly to the hazard at long periods while the TMVB sources contribute mostly at the short periods. Since the spectral shapes vary considerably depending on the source, scenario spectra (rather than uniform hazard response spectra) were developed to more realistically characterize the ground motion input.

1 INTRODUCTION plateau is located within the Trans-Mexican Volcanic Belt (TMVB), a complex Tertiary and Quaternary feature, which A probabilistic seismic hazard assessment (PSHA) is often crosses the country from the Pacific to the Atlantic Oceans. carried out in developing design ground motions, providing The region is subject to natural hazards such as floods, “hazard-consistent” ground-motion intensity (often in a volcanic eruptions, and earthquakes. form of pseudo-spectral acceleration) along with the associated hazard contributions via hazard deaggregation. 2.1 Tectonic Setting This information is used as key input for developing design response spectra suitable for a desired site. This study Mexico is located along the Circumpacific Belt, the highest presents a PSHA performed for a confidential high-profile seismicity region worldwide. The tectonic map of Mexico is project in Mexico City (see Figure 1). The seismic hazard shown in Figure 2. The major source of earthquake hazard is calculated for the “rock” level of the project site, where to Mexico City is the subduction zone of the Pacific Ocean, the rock corresponds to the shear wave velocity (Vs) of where the Cocos plate subducts beneath the North about 600 m/s and is approximately 180 m below ground America plate. The subduction zone of Mexico is usually surface. The results of this study are used as rock input divided into the Jalisco, Michoacán, Guerrero, and Oaxaca motions to carry out site-specific seismic soil response blocks from north to south. The Rivera plate is subducting analyses to calculate the motions at the surface/foundation beneath the Jalisco block at rates of 20–50 mm per year in level for non-linear response history analysis. The resulting the northeast direction (Kostoglodov and Bandy 1995), and surface/foundation motions are then, utilized to carry out the Cocos plate beneath the other three blocks at rates of the performance-based design of the project buildings. 50–70 mm per year in the northeast direction (DeMets et al. 1990). In general, the seismicity associated with the slab 2 TECTONIC AND GEOLOGIC SETTING is shallower than about 100 km, and shows rapid lateral variations in dip at depths. A Wadati-Benioff in the Jalisco Mexico City is located in a unique geological and structural region has a relatively steep dip angle of about 50˚ to the setting, on a volcanic high plateau at about 2,240 m above maximum depth of about 130 km (Pardo and Suárez 1995). sea level, bounded by volcanic sierras, alluvial fans and Toward the south, the westernmost region of the Cocos plains (Flores-Estrella et al. 2006). The deep basement structure is faulted and folded, and these structural features contribute to the basin seismic response. The

Figure 1. Mexico City location (red box), final earthquake catalogue and USGS focal depth contours (Slab model; Hayes et al. 2012); the dashed line shows the search boundary for the earthquake catalogue. plate has a relatively gentle dip angle of about 30°. In the in the TMVB include the 1567 Ameca, Jalisco, earthquake regions of Guerrero and Oaxaca, the subducted slab (MW7.2; Suter 2015), the 1912 Acambay earthquake becomes almost flat at about 40–70 km depth range (e.g. (MW6.8-7.0; Langridge et al. 2000). Pérez-Campos et al. 2008). In the Isthmus of Tehuantepec region, the interface seismicity defines a Wadati-Benioff 2.2 Geological Features zone at the dip angle of about 30° (Pardo and Suárez 1995). Mexico City is located in the basin of Mexico, which The Mexican subduction zone extends over about 1000 previously contained a number of lakes. The lakes were km along the Middle-America trench, from the Jalisco- drained to allow density growth of the population. The Colima region through the Michoacán-Guerrero region to unique geological conditions of the Valley of Mexico were the Oaxaca region. It appears to be segmented by the investigated by a number of researchers to understand the Rivera fracture zone, the East Pacific Rise, the Orozco and background to seismic activity, hydraulic nature of the O’Gorman fracture zones, and the Tehuantepec ridge, basin and petroleum geology. The geological conditions (Singh and Mortera 1991). A number of large magnitude were explained by, among others, Marsal and Mazari events (moment magnitude, MW>7.0) occurred from the (1959), Mooser (1963), and Zeevaert (1991). Jalisco-Nayarit boundary to the west of Chiapas including the 1932 Jalisco earthquake (Surface-wave magnitude, 3 EARTHQUAKE CATALOGUE MS=8.2; the largest instrumentally-recorded earthquake in Mexico), the 1985 Michoacán earthquake (MW=8.0), the The study area for compiling the earthquake catalogue is 1995 Colima-Jalisco earthquake (MW=8.0), and the 2003 bounded by Latitudes 11.09°N to 23.86°N and Longitudes Colima earthquake (MW=7.5). 90.03°W to 112.02°W (see Figure 1). The following six In addition to the subduction sources, the Trans- earthquake databases are used (range of dates covered in Mexican Volcanic Belt (TMVB) is an important seismic parentheses): source even though it has relatively low seismicity. The 1. International Seismological Centre - Global Earthquake TMVB is a Miocene to recent volcanic arc transecting Model, ISC-GEM Global Instrumental Earthquake central Mexico from the Pacific coast to the Gulf of Mexico Catalogue (1902–2011; Storchak et al. 2012) – (see Figure 2). This intracontinental region has active faults abbreviated as “GEM2015” with relatively low deformation rates. The low seismicity 2. GEM Global Historical Earthquake Archive (1000–1903) rate of the region has led to an increasing use of paleo- – abbreviated as “GEM_Hist” seismological tools in identifying destructive earthquakes 3. The Bulletin of the International Seismological Centre (Ortuño et al. 2015). The significant historical earthquakes (1900–2012) – abbreviated as “ISC”

originally proposed by Stepp (1972). In this method, the number of earthquakes per year exceeding a given magnitude is computed for various sub-catalogues (e.g., 2005-2015, 2000-2015 and so on). If a dataset is complete, the annual number (average rate) of earthquakes greater than each magnitude will be the same for a range of time periods (assuming there are no temporal trends in the level of seismicity). Table 1 lists the resulting completeness periods, and Figure 3 shows the earthquake MW distribution with years.

Table 1. Completeness period

Completeness M period W Figure 2. Tectonic Map of Mexico (modified from Santoyo 1731 to 2015 ≥ 7.5 et al. 2006) 1736 to 2015 ≥ 7.0 1901 to 2015 ≥ 6.5 4. Engdahl, Hilst and Buland (1960–2008) – processed 1921 to 2015 ≥ 6.0 version of the ISC database – abbreviated as “EHB” 1951 to 2015 ≥ 5.5 5. National Oceanic and Atmospheric Administration 1966 to 2015 ≥ 5.0 Global Significant Earthquake Database (2150 BC– 1986 to 2015 ≥ 4.0 Present) – abbreviated as “NOAA” 6. United States Geological Survey Earthquake Archives (1900–Present) – abbreviated as “USGS” For the search boundary, the oldest event in our compiled catalogue is the year 1527, and the total number of the “raw” data points is about 37,000. Since the raw catalogue was compiled from multiple sources, some data points are duplicated. All the duplicates were removed by comparing the time, location, depth, and magnitude of the potential duplicate events. The dataset with no duplicates contains different types Figure 3. Earthquake MW distribution with years; the red of magnitudes. We performed magnitude conversions to line shows the completeness thresholds MW for a catalogue with a uniform magnitude since the ground motion prediction equations (GMPEs) are in terms 4 SOURCE CHARACTERIZATION of MW. All data with an MW was assigned directly as MW values for the uniform magnitude catalogue. For the There are three types of source zones modeled in the remaining data, we converted the other magnitude types to analysis: MW using the existing correlations, and verified the  Subduction–Interface: Large earthquakes are generated correlation equations work well for our compiled data set. between the subduction of Cocos and Rivera oceanic If no correlation equation was available, we developed a plates beneath the North American continental plate. conversion equation using our collated catalogue. From the south of Sinaloa to the west of Chiapas large All catalogues contain some foreshock and aftershock earthquakes (MW>7) occur with relatively short time of sequences. To carry out a probabilistic analysis for seismic recurrence. The significant earthquakes that occurred in hazard, using a Poissonian process, all earthquake events this region include the 1932 Jalisco earthquake (MW8.1), are considered statistically independent, and therefore the the 1985 Michoacán earthquake (MW8.0), and the 1995 fore- and aftershocks must be removed from the catalogue. Colima-Jalisco earthquake (MW8.0). Also, a very large We used a windowing procedure by Gardner and Knopoff historical earthquake occurred in 1787 with an estimated (1974) to remove foreshocks and aftershocks. The moment magnitude of MW8.6 (Suárez and Albini 2009). procedure relates the maximum possible distance and time  Subduction – Intraslab: Large earthquakes also occur in of an aftershock to the main shock magnitude (i.e. spatial the Mexican continent at depths around 60 km or deeper. and temporal criteria). After the aftershock and foreshock They are mostly caused by normal fault mechanisms removal, the catalogue consists of 1,847 events (main within the subducted ocean plate (Singh et al. 1985). shocks). The complete catalogue is shown in Figure 1. Also These earthquakes are relatively infrequent but they shown in Figure 1 is the Slab model (contours) for Mexican caused large damage (Ordaz et al. 2000). subduction zone (Hayes et al. 2012; USGS 2011). The  Crustal earthquakes: More rare are the crustal focal depth distribution of our catalogue is in good earthquakes, which occur within the continental plate. agreement with the Slab model. Such events may cause also considerable damage. We assessed the statistical completeness of the Earthquakes of this kind are the 1567 Ameca, Jalisco, earthquake catalogue through a procedure similar to that earthquake (MW7.2; Suter 2015), the Acambay

November 19, 1912 (MW6.8-7.0; Langridge et al. 2000), (2014; AEA14) to account for regional uncertainty in and the Jalapa January 3, 1920 (MW=6.4; Suárez 1992). shallow tectonic ground motions. We applied the weights of 0.83 and 0.17 to the NGA-West2 models (Table 3) and Figure 4 shows the source models consisting of nine Akkar et al. (2014), respectively. area sources (A1 to A7) and six fault sources of dipping planes (S1 to S6), developed based on characteristics of Table 2. Recurrence parameters and maximum seismicity, geologic and tectonic settings. The fault magnitudes; S1 through S6 for subduction and A1 through sources, S1 to S3 represent the interface subduction zones A7 for shallow crustal source zones while S4 to S6 represent the intraslab subduction zones with deep focal depths greater than 40 km. They are Activity Rate b-value modelled as dipping planes. Their average dip angles were Zone (N ≥ MW4.0 per year) Mmax determined based on Slab1.0, a three-dimensional model Mean σ Mean σ of global subduction zone geometries (Hayes et al. 2012; S1 0.88 0.06 5.07 0.53 8.1 Figure 1), ranging about 30° to 40°. The area sources, A1 S2 0.60 0.02 7.19 0.41 8.8 to A7, represent the shallow crustal zones, including A6-2 S3 0.85 0.03 17.25 0.96 9.1 and A6-3 representing the TMVB region. S4 0.65 0.06 2.57 0.31 8.6 S5 0.68 0.04 3.70 0.35 8.2 S6 0.81 0.02 37.37 1.38 8.4 A1 0.65 0.04 5.06 0.44 7.2 A2 0.67 0.06 2.68 0.33 7.1 A3 0.81 0.08 2.27 0.34 8.4 A4 0.74 0.10 1.12 0.18 6.8 A5 0.85 0.07 4.19 0.47 7.9 A6-1 1.03 0.14 0.38 0.11 5.3 A6-2 0.90 0.18 0.76 0.21 7.7 A6-3 0.80 0.20 0.75 0.20 7.1 A7 0.65 0.14 0.25 0.08 5.9

Then, we equally distributed 0.83 to the four individual NGA-West2 models (thus, 0.208 for each). We assigned a larger weight (0.83) to the NGA-West2 because it included Mexican records while the Akkar et al. model was derived

Figure 4. Source Models: A1 – A7 are the area source while primarily from European ground motion records. It is noted S1 through S6 are the fault sources that including Akkar et al. (2014) as a shallow crustal GMPE has negligible impact on the hazard results, based

The magnitude recurrence parameters, N(mo) and b on our sensitivity analyses (0.34 versus 0.17 for Akkar et value were derived for each zone based on Weichert al., 2014), which is not presented herein. However, we (1980). In addition, the maximum magnitudes (Mmax) were decided to include Akkar et al. (2014) for variability of derived based on the observed maximum magnitude +0.2 ground motions. Note there are no local models for shallow and +0.5 units for shallow crustal and subduction source crustal earthquakes. Furthermore, few recorded shallow zones, respectively. This added unit was judged crustal strong motions are available, which make it difficult appropriate for epistemic uncertainty in Mmax. We also to evaluate the GMPEs. The current shallow crustal considered a normal distribution around the maximum GMPEs should be evaluated when strong motion records magnitude such that +/-1 standard deviation (σ) from local shallow crustal sources become available. correspond to +0.2/-0.2 units about the maximum magnitude. This is described in more detail in Section 6. Table 3. Selected ground motion prediction equations The parameters used in the PSHA are listed in Table 2. (GMPEs) and their weights used in this study We also developed focal depth distribution (probability density) models for individual area sources using the Region GMPE Weight processed earthquake data associated with each area Subduction – Reyes (1999); REY99 1.0 source. However, these models are not presented in this Interface paper due to the limited space. Subduction – Jaimes et al. (2015); JEA15 1.0 Intraslab 5 GROUND MOTION PREDICTION EQUATION NGA-West2*: Abrahamson et al. (2014); Table 3 lists the GMPEs used in the PSHA herein along ASK14 with the weighting scheme. Shallow Boore et al. (2014); BSSA14 0.83 For shallow crustal models, we considered the widely Crustal Campbell & Bozorgnia (2014); accepted NGA-West2 models including Abrahamson et al. CB14 (2014; ASK14); Boore et al. (2014; BSSA14); Campbell & Chiou & Youngs (2014); CY14 Bozorgnia (2014; CB14); and Chiou & Youngs (2014; Akkar et al. (2014); AEA14 0.17 CY14). We also included a European model, Akkar et al. *Equal weight for individual GMPEs.

For subduction models, we adopted local models, The logic tree approach was employed to represent the Reyes (1999) GMPE for interface events and a recent epistemic uncertainties in estimating the following model by Jaimes et al. (2015) for intraslab events, which variations. outperformed the global subduction GMPEs including Allowance for variation in the b-value and activity rate in Abrahamson et al. (2015), Zhao et al. (2006), and Atkinson all zones was incorporated in the seismic model by & Boore (2003; 2008) in comparison with recorded data. assigning weights of 60% to mean and 20% each to Generally, the local GMPEs capture the unique spectral mean ± 1.6 σ as given in Table 2, broadly following a shape exhibiting rich long-period content even for rock normal distribution suggested by Keefer and Bodily motions due to the local geological strata with interbedded (1983). clay and tuff deposits forming the Tarango Formation Allowance was made for variability of maximum (referred to a companion paper, Kumar et al. 2017) while magnitude in the different zones by attributing weights of the global GMPEs significantly underestimate the long- 60% to mean and 20% each to the mean ± σ Mmax of 0.2 period content. This is based on our GMPE evaluation in Table 2. For example, for source S3, the considered performed with the recorded motions in Mexico City from mean Mmax equals MW9.1 and the +/- 1σ values equal MW≥6.5 subduction events available in the Mexican Strong MW9.3 and MW8.9, respectively. Motion Database (Alcántara et al., 2000); this evaluation is The weights corresponding to the selected GMPEs are not presented herein due to the limited space. summarized in Table 3. This was presented in Section 5. Both local GMPE models were derived based on data recorded at the surface of Ciudad Universitaria station (a firm site in the city); abbreviated as CU. The CU site has an approximately 15 m-thick soil layer (of about 150 to 200 m/s) overlying the rock (Tarango Formation with a Vs of about 600 m/s on average). The overlying soil causes amplifications from the rock level mainly at spectral periods (T) less than about 0.5 sec. Consequently, the corresponding period accelerations per the two local GMPEs will be overestimated relative to the Tarango layer. For that reason, we performed de-convolution of the CU site per EPRI (1988) and applied the spectral ratios to the surface target spectra resulting from the local models. We also applied a constraint to the magnitude scaling for large magnitudes, adopting the method of Abrahamson et al. (2015). We found that in the course of incorporating the local subduction zone GMPEs into the PSHA, the resulting response spectra were unreasonably high for large magnitude events. We discovered that this was caused by the fact that the local GMPEs have their functional form assuming the same linear magnitude scaling (in a natural log unit) without constraints for large magnitude. The global subduction GMPE by Abrahamson et al. (2015) constrains the magnitude scaling for large events using a bi-linear magnitude scaling model with a magnitude break of MW7.8. Due to the lack of large subduction events, the magnitude scaling Abrahamson et al. (2015) used for large events was based on the Figure 5. Comparison of magnitude scaling terms: numerical simulations (Gregor et al., 2002; Atkinson and Abrahamson et al. (2015); Jaimes et al. (2015); and the Macias, 2009). The simulations showed a weaker modified Jaimes et al. (2015) model for periods of 0.2 sec and 1.0 sec magnitude scaling for large (MW>8.0) magnitudes. We modified the Reyes (1999) and Jaimes et al. (2015)

GMPEs by adopting the slope of the magnitude scaling 7 SEISMIC HAZARD ASSESSMENT RESULTS term derived by Abrahamson et al. (2015) beyond the largest recorded magnitude used by Reyes and Jaimes et The probabilistic seismic hazard calculations were carried al. in their data regression analysis. For example, Figure 5 out using an in-house program, Oasys SISMIC (Oasys, shows the modified Jaimes et al. (2015) model, where the 2015). Figure 6 shows the uniform hazard response slope was altered to match Abrahamson et al. (2015) spectra (5% damping), UHRS, at rock (Vs of about 600 beyond MW7.4 (corresponding to the 1999, September 30 m/s) for the return periods of 475, 975, and 2,475 years. earthquake). Also shown in Figure 5 for comparison are the The tabulated UHRS are provided in Table 4. For original Jaimes et al. (2015) and Abrahamson et al. (2015) comparison, the rock PGA range associated with the return models. period of 475 years estimated by GSHAP (Global Seismic

Hazard Assessment Program; Giardini et al. 1999) is 0.08 6 LOGIC TREE g to 0.24 g for Mexico City area, which encompasses our

estimate of 0.12 g.

We performed hazard deaggregation in terms of source Table 6. Most hazard-contributing MW and R pairs per type, moment magnitude (MW) and source-to-site distance source type, and their associated epsilon (center value of (R; epicentral distance). Table 5 lists the percent hazard bin); the most-contributing source in parentheses contribution for each source type, and Table 6 summarizes the modal MW and R pairs per source type and the 0.2 0.4 0.5 0.75 1.0 2.0 3.0 4.0 associated epsilons. In addition, Figure 7 and Figure 8 Source Type sec sec sec sec sec sec sec sec show the percent hazard contributions of different MW and Mw/R (km) [epsilon] Shallow 6.6/ 6.6/ 6.6/ 6.6/ R pairs associated with the return period 2,475 years for 6.6/ crustal 25* 25* 25* 25 N.A. N.A. N.A. T=0.2 and 1.0 sec, respectively. In general, the largest 25 hazard contribution for relatively short periods (0.2 sec) is (A6-3) [1.0] [1.0] [1.25] [1.5] 7.6/ 7.6/ 7.6/ Subduction; 7.6/ 7.6/ 7.6/ from R=0–50 km, which corresponds to the shallow crustal N.A. N.A. 175 175* 175* in-slab (S5) 175* 175* 175* zone (A6-3) while for long periods (≥1 sec), most of the [2.5] [2.25] [2.25] hazard is from R=150–200 km and 300–350 km 8.6/ Subduction; 8.6/ 8.6/ corresponding to the interface zone (S2) and the intraslab N.A. N.A. N.A. N.A. N.A. 325 interface (S2) 325 325 zone (S5), respectively. [2.75] * modal MW and R N.A. Not available due to small contribution (<10%) Number of epsilon is shown for T=0.2 sec, 0.4 sec, 0.5 sec, 1.0 sec, and 2.0 sec.

Figure 6. Uniform hazard response spectra (5% damping) at rock (Vs ~ 600 m/s) for the return periods of 475, 975, and 2,475 years

Table 4. Uniform hazard response spectra (g)

Figure 7. Hazard deaggregation in terms of moment T (sec) 475 years 975 years 2,475 years magnitude and source-to-site distance for the return period 0.01 0.120 0.166 0.258 of 2,475 years: T=0.2 sec 0.2 0.271 0.376 0.574 0.4 0.167 0.233 0.359 0.5 0.169 0.227 0.326 0.75 0.171 0.223 0.305 1 0.160 0.207 0.281 2 0.137 0.167 0.215 3 0.084 0.103 0.132 4 0.057 0.071 0.093

Table 5. Hazard contribution at different periods (T) per source type for return period of 2,475 years

Source 0.2 0.4 0.5 0.75 1.0 2.0 3.0 4.0 Type sec sec sec sec sec sec sec sec Shallow crustal 96 96 77 39 23 6 4 3 (A6-3) Subduction; 4 4 23 61 77 72 63 89 in-slab (S5) Subduction; interface 0 0 0 0 0 22 32 8 Figure 8. Hazard deaggregation in terms of moment (S2) magnitude and source-to-site distance for the return period of 2475 years: T=1.0 sec

8 SCENARIO EARTHQUAKE SPECTRA 10 ACKNOWLEDGEMENTS

According to the deaggregation results (Table 5), shallow We would like to thank Gerardo Suárez and Jonathan Bray crustal sources contribute most of the total hazard for for their comments to improve this work. Also, we thank T≤0.5 sec while subduction sources (primarily intraslab) Juan Mayoral and Francisco Ciruela-Ochoa for their help govern the hazard for longer periods. Each of the source on the Mexican Strong Motion Database and GIS tools, types produces distinct spectral shapes (Figure 9). Thus, respectively. we developed a suite of scenario earthquake spectra based on the deaggregation results, to envelope the UHRS 11 REFERENCES over the period range of interest. This approach yields realistic ground motions for design, and enables the Abrahamson, N.A., Silva, W.J., and Kamai, R. 2014. selection of recorded motion time histories, which after Summary of the ASK14 ground motion relation for spectral matching, will retain their original characteristics. active crustal regions, Earthquake Spectra, 30: 1025- Using the same GMPEs and the weighting scheme 1055. (Table 3) as used in the PSHA, the individual scenario Abrahamcon, N.A., Gregor, N., and Kofi, A. 2015. BC earthquake spectra were developed for their controlling MW Hydro ground motion prediction equations for and R pairs, and epsilons in Table 6. Figure 9 shows the subduction earthquakes, Earthquake Spectra, doi: resulting scenario earthquake spectra. Note that their http://dx.doi.org/10.1193/051712EQS188MR, in-press, envelope are comparable to the UHRS. These three Akkar, S., Sandikkaya, M.A., and Bommer, J.J. 2014. scenario earthquake spectra can be used as target Empirical ground-motion models for point- and response spectra in developing design motion time extended-source crustal earthquake scenarios in histories, which are inputs to site-specific response Europe and the Middle East, Bull. Earthquake Eng. 12: analyses and soil-structure interaction analyses. 359-387. Alcántara, L., Quaas, R., Pérez, C., Ayala, M., Macías, M.A., Sandoval, H., Javier, C., Mena, E., Andrade, E., González, F., Rodríguez, E., Vidal, E., Murguía, L., Luna, M., Espinoza, J. M., Cuellar, A., Camarillo, L., Ramos, S., Sánchez, M., Guevara, E., Flores, J.A., López, B., Ruiz, R., Pacheco, J., Ramírez, M., Aguilar, J., Juárez, J., Vera, R., Gama, A., Cruz, R., Hurtado, F., Martín del Campo, R., and Vera, R. 2000. Mexican Strong Motion Database, CD-rom v2, Mex. Soc. of Seis. Engrg. Atkinson, G.M. and Boore, D.M. 2003. Empirical ground- motion relations for subduction-zone earthquakes and their application to Cascadia and other regions. Bulletin of the Seismological Society of America, 93(4): 1703-1729. Atkinson, G.M. and Boore, D.M. 2008. Erratum to Empirical ground-motion relations for subduction-zone

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