TY - JOUR A1 - Pilz, Marco A1 - Cotton, Fabrice A1 - Zhu, Chuanbin T1 - How much are sites affected by 2-D and 3-D site effects? BT - a study based on single-station earthquake records and implications for ground motion modelling JF - Geophysical journal international N2 - 1-D site response analysis dominates earthquake engineering practice, while local 2-D/3-D models are often required at sites where the site response is complex. For such sites, the 1-D representation of the soil column can account neither for topographic effects or dipping layers nor for locally generated horizontally propagating surface waves. It then remains a crucial task to identify whether the site response can be modelled sufficiently precisely by 1-D analysis. In this study we develop a method to classify sites according to their 1-D or 2-D/3-D nature. This classification scheme is based on the analysis of surface earthquake recordings and the evaluation of the variability and similarity of the horizontal Fourier spectra. The taxonomy is focused on capturing significant directional dependencies and interevent variabilities indicating a more probable 2-D/3-D structure around the site causing the ground motion to be more variable. While no significant correlation of the 1-D/3-D site index with environmental parameters and site proxies seems to exist, a reduction in the within-site (single-station) variability is found. The reduction is largest (up to 20 per cent) for purely 1-D sites. Although the taxonomy system is developed using surface stations of the KiK-net network in Japan as considerable additional information is available, it can also be applied to any (non-downhole array) site. KW - Earthquake ground motions KW - Earthquake hazards KW - Site effects KW - Wave propagation Y1 - 2021 U6 - https://doi.org/10.1093/gji/ggab454 SN - 0956-540X SN - 1365-246X VL - 228 IS - 3 SP - 1992 EP - 2004 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Dahm, Torsten A1 - Heimann, Sebastian A1 - Metz, Malte A1 - Isken, Marius Paul T1 - A self-similar dynamic rupture model based on the simplified wave-rupture analogy JF - Geophysical journal international / the Royal Astronomical Society, the Deutsche Geophysikalische Gesellschaft and the European Geophysical Society N2 - The investigation of stresses, faults, structure and seismic hazards requires a good understanding and mapping of earthquake rupture and slip. Constraining the finite source of earthquakes from seismic and geodetic waveforms is challenging because the directional effects of the rupture itself are small and dynamic numerical solutions often include a large number of free parameters. The computational effort is large and therefore difficult to use in an exploratory forward modelling or inversion approach. Here, we use a simplified self-similar fracture model with only a few parameters, where the propagation of the fracture front is decoupled from the calculation of the slip. The approximative method is flexible and computationally efficient. We discuss the strengths and limitations of the model with real-case examples of well-studied earthquakes. These include the M-w 8.3 2015 Illapel, Chile, megathrust earthquake at the plate interface of a subduction zone and examples of continental intraplate strike-slip earthquakes like the M-w 7.1 2016 Kumamoto, Japan, multisegment variable slip event or the M-w 7.5 2018 Palu, Indonesia, supershear earthquake. Despite the simplicity of the model, a large number of observational features ranging from different rupture-front isochrones and slip distributions to directional waveform effects or high slip patches are easy to model. The temporal evolution of slip rate and rise time are derived from the incremental growth of the rupture and the stress drop without imposing other constraints. The new model is fast and implemented in the open-source Python seismology toolbox Pyrocko, ready to study the physics of rupture and to be used in finite source inversions. KW - Earthquake dynamics KW - Earthquake ground motions KW - Earthquake hazards KW - Earthquake source observations Y1 - 2021 U6 - https://doi.org/10.1093/gji/ggab045 SN - 0956-540X SN - 1365-246X VL - 225 IS - 3 SP - 1586 EP - 1604 PB - Oxford Univ. Press CY - Oxford ER -