Seismic Performance of Slopes Subjected to Earthquake Mainshock Aftershock Sequences

Authors: Alisha Khanal, Gokhan Saygili

Abstract:

It is commonly observed that aftershocks follow the mainshock. Aftershocks continue over a period of time with a decreasing frequency and typically there is not sufficient time for repair and retrofit between a mainshock–aftershock sequence. Usually, aftershocks are smaller in magnitude; however, aftershock ground motion characteristics such as the intensity and duration can be greater than the mainshock due to the changes in the earthquake mechanism and location with respect to the site. The seismic performance of slopes is typically evaluated based on the sliding displacement predicted to occur along a critical sliding surface. Various empirical models are available that predict sliding displacement as a function of seismic loading parameters, ground motion parameters, and site parameters but these models do not include the aftershocks. The seismic risks associated with the post-mainshock slopes ('damaged slopes') subjected to aftershocks is significant. This paper extends the empirical sliding displacement models for flexible slopes subjected to earthquake mainshock-aftershock sequences (a multi hazard approach). A dataset was developed using 144 pairs of as-recorded mainshock-aftershock sequences using the Pacific Earthquake Engineering Research Center (PEER) database. The results reveal that the combination of mainshock and aftershock increases the seismic demand on slopes relative to the mainshock alone; thus, seismic risks are underestimated if aftershocks are neglected.

Keywords: Seismic slope stability, sliding displacement, mainshock, aftershock, landslide, earthquake.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.2702809

References:

[1] Andersen, K. H. (2015). Cyclic soil parameters for offshore foundation design. Frontiers in Offshore Geotechnics III.
[2] Antonakos, G. 2009. Models of Dynamic Response and Decoupled Displacements of Earth Slopes during Earthquakes. PhD Thesis, Austin, Tx: University of Texas at Austin.
[3] Boore, M. B., Stewart P. J., Seyhan E., and Atkinson M. G. 2014. "NGA-West 2 Equations forPredicting PGA, PGV, and 5% Damped PSA for Shallow Crustal Earthquakes." Earthquake Spectra 1057-1085.
[4] Chiou, B., Darragh, B., & Power, M. (2005). NGA Documentation. Nation Geospatial-Intelligence Agency (NGA).
[5] Goda, K. 2014. "Record selection for aftershock incremental dynamic analysis." Earthquake Engineering and Structural Dynamics.
[6] Han, R., Y. Li, and J. Lindt. 2014. "Seismic risk of base isolated non-ductile reinforced concrete buildings considering uncertainties and mainshock-aftershock sequences." Structural Safety 39-56.
[7] Jeon, J., R. DesRoches, L. N. Lowes, and I. Brilakis. 2015. "Framework of aftershock fragility assessment–case studies: older California reinforced concrete building frames." Earthquake Engineering and Structural Dynamics.
[8] Jibson, R. W., E. M. Rathje, M. W. Jibson, and Y. W. Lee. 2013. Seismic Landslide Movement Modeled using Earthquake Records. Software Manual, United States Department of the Interior, United States Geological Survey.
[9] Kim, C., Smell, C., & Medley, E. (2004). Shear Strength of Franciscan Complex Melange as Calculated from Back-Analysis of a Landslide. Geotechnical Engineering Commons. Missouri: Missouri University of Science and Technology Scholar's Mine.
[10] Kottke, A. R., & Rathje, E. M. (2009). Technical Manual for Strata. California: Pacific Earthquake Engineering Reseach Center.
[11] Li, Y., R. Song, and J. W. Van De Lindt. 2014. "Collapse Fragility of Steel Structures Subjected to Earthquake Mainshock-Aftershock Sequences." Journal of Structural Engineering 140(12) Collapse Fragility of Steel Structures Subjected to Earthquake Mainshock-Aftershock Sequences.
[12] PEER Ground Motion Database. (2014). Retrieved 2018, from https://ngawest2.berkeley.edu/.
[13] Raghunandan, M., Liel, A. B., & Luco, N. (2015). Aftershock collapse vulnerability assessment of reinforced concrete frame structures. Earthquake Engineering & Structural Dynamics, 44(3), 419-439.
[14] Rathje, E. M., and J. D. Bray. 2001. "One- and two-dimensional seismic analysis of solid-waste landfills." Canadian Geotechnical Journal, 38 850-862.
[15] Rathje, E. M., Wang, Y., Stafford, P. J., Antonakos, G., & Saygili, G. (2014). Probabilistic assessment of the seismic performance of earth slopes. Bulletin of Earthquake Engineering, 12(3), 1071-1090.
[16] Rathje, E. M., & Antonakos, G. (2011). A unified model for predicting earthquake-induced sliding displacements of rigid and flexible slopes. Engineering Geology, 122(1-2), 51-60.
[17] Ruiz-García, J., and J. C. Negrete-Manriquez. 2011. "Evaluation of drift demands in existing steel frames under as-recorded far-field and near-fault mainshock–aftershock seismic sequences." Engineering Structures 621-634.
[18] Ruiz-Gracia, J., and J., D. Aguilar. 2017. "Influence of modeling assumptions and aftershock hazard level in seismic response of post-mainshock steel framed buildings." Engineering Structures, 140 437-446.
[19] SAS. 2018. "JMP." Computer Software.
[20] Saygili, G., and E. M. Rathje. 2008. "Empirical Predictive Models for Earthquake Induced Sliding Displacement of Slopes." Journal of Geotechnical and Geoenvironmental Engineering 790-803.
[21] Song, R., Y. Li, and J. W. Van de Lindt. 2014. "Impact of earthquake ground motion characteristics on collapse risk of post-mainshock buildings considering aftershocks." Engineering Structures.
[22] Tiwari, B., Brandon, L. T., Marui, H., & Tuladhar, R. G. (2005). Comparison of Residual Shear Strengths from Back Analysis and Ring Shear Tests on Undistrurbed and Remodeled Specimens. ASCE.
[23] Vrymoed, J. L., and E. R. Calzascia. 1978. "Simplified determination of dynamic stresses in earth dams." Earthquake Engineering and Soil Dynamics. New York: ASCE. 991-1006.
[24] Wu, J.-H., & Tsai, P.-H. (2011). New dynamic procedure for back-calculating the shear strength parameters of large landslides. Engineering Geology 123, 129-147.
[25] Yin, Y., J., and Y. Li. 2010. "Seismic collapse risk of light-frame wood construction considering aleatoric and epistemic uncertainties." Structural Safety 32(4) 250-261.