Near-fault observation and simulation of earthquake ground motion in an urban environment – E-CITY
Tracking the temporal and spatial variability of the strong ground motion near the seismic source
Ground motion produced in the vicinity of the fault can strongly be modified not only by the rupture itself, but also by the mechanical properties of the shallow material. These effects are the so-called nonlinear site response, and they are responsible for modifying the expected seismic hazard computed by traditional methods.
The general objective is how to characterize the ground motion affected by nonlinear effects. What do we obtain with this? We have an in-situ estimation of the material mechanical properties.
The main objectives are (1) description of the initial stress state in the vicinity of the fault. (2) Extracting the dynamic properties of the shallow crust using only seismic observations. (3) Study of the near-field ground motion at the city scale, this is the so-called soil-city interaction. The main issues that we found are the lack of detailed knowledge of the regions. There are few places in the world where geophysical, geological and seismological information are collected to fully characterize a region. We work most of the time blindly and finding our way by trail-and-error based on few observations, in particular for WP1 because there is no direct access to the fault itself. An important issue concerning the dynamic properties of the shallow structure is that this information comes from laboratory tests on disturbed samples. WP2 develop a method to extract this information in-situ using earthquake data. We find that there are some discrepancies, in particular, the description from the lab is using the strains, and the description from the field uses the acceleration. We still need to conceal these results, so they can be used together in the seismic hazard estimation when nonlinear site response is needed. WP3 raised the issue of what happens to a building and therefore to a collection of buildings when an earthquake strikes the city. The orientation and location of buildings may drive the incoming wavefield as metamaterials do. We might think that is beneficial for the city, sometimes yes because the intensity of the ground motion is reduced at some frequencies. Yet, the energy is preserved, and there are other places where this energy appears. Thus, we track the evolution of the building response as a diffusive effect, which mainly affects the damping. The problem we have is to how to faithfully represent a city, and where the seismic sources are located to study these effects more realistically. Another important issue is that the numerical simulations cannot go to higher frequencies due to the lack of knowledge at these frequencies and the computer power. For this reason, we still rely on observations from stations located in buildings in urban areas.
WP1: The computation of the initial stress state and the numerical simulations of wave propagation use the state-of-art, namely, the spectral element method. Depending of the size of the region analyzed, a cluster of computers is definitely needed. This is a shortcoming for small engineering cabinets, they are not equipped with this technology. Yet, this gap will decrease in the future with new technologies such as the GPU.
WP2: The reconstruction of the Green's functions from earthquake data relies in the method of seismic interferometry. This WP developed new techniques that make this computation more robust and effective. Needless to say, the amount of data used, 22 years of data, in almost 60 stations in a single prefecture in Japan needed some computer hours to complete the analysis. The extension to 500 stations in the whole country made this task longer, but still doable in a multicore PC. Yet, for reevaluation of hundreds of stations in a given region, a cluster might also be a good idea, not only for speed, but also for the storage needed for years of available data.
WP3: Earthquake data of instrumented building in weak-to-strong seismic prone region (France, to Japan). Dense nodal seismic network now applied to geophysical scale for metamaterial analysis.
Ambient vibration and modal analysis.
List of publications WP1:
H. Aochi, V. M. Cruz-Atienza. Rupture Dynamics and Near-Fault Ground Motion of the Mw7.8 Kahramanmaraş, Turkey earthquake of February 6, 2023. Seismica, 2025, 4 (1), ⟨10.26443/seismica.v4i1.1432⟩.
F. Dupros, S. Jubertie, H. Aochi. A Preliminary Study on Performance Modeling at Scale for Geophysical Applications. 33rd Euromicro International Conference on Parallel, Distributed, and Network-based Processing (PDP 2025), Mar 2025, Turin (IT), Italy.
H. Aochi. Dynamic rupture inversion on the M5.9 pre-event before the 2024 M7.6 Noto-Peninsula, Japan, earthquake. EPS 2024, 76 (1), pp.148. ⟨10.1186/s40623-024-02095-4⟩.
H. Aochi. Near-field ground motion and dynamic rupture process. GSEV - V Colloquium on Geophysical Signatures of Earthquakes and Volcanoes and Workshop "Earthquakes: from observations to dynamic rupture simulations", Santiago, May 2023, Santiago (CL), Chile.
H. Aochi, K. Tsuda. Dynamic rupture simulations based on depth-dependent stress accumulation. GJI, 2022, ⟨10.1093/gji/ggac453⟩.
List of publications WP2:
S. Lai, A. Schibuola, L. F. Bonilla, Unveiling nonlinear site response through time-frequency analysis of earthquake records, GJI, Vol 241, Issue 3, June 2025, Pages 1601–1632, doi.org/10.1093/gji/ggaf098
A. Schibuola, S. Lai, L. F. Bonilla, E. Stutzmann, M. Schimmel, Estimating subsurface velocity and resonance frequency changes using two decades of KiK-net data in the Iwate Prefecture, Japan, GJI, Vol 245, Issue 2, May 2026, doi.org/10.1093/gji/ggag088
Flores‐Allende, R., Seydoux, L., Beaucé, É., Bonilla, L. F., Gueguen, P., & Satriano, C. (2026). Fine‐scale segmentation and spatiotemporal variability of the 2010 Mw 8.8 Maule aftershock sequence revealed by
a deep‐learning‐based earthquake catalog. JGR, 131, e2026JB034262. doi.
List of publications WP3:
Guéguen P., Astorga A. 2024. Using In-Building observations of small-to-large earthquakes to predict the seismic response of structures, BSSA 114 (6): 3063–3077, doi: 10.1785/0120240036
Celorio, M., Guéguen, P., Aochi, H., De Martin, F., & Bonilla, L. F. 2025. Urban Attenuation Lengths in City‐Like Environments: Insights from 3D Numerical Simulations of Site–City Interaction. BSSA doi: 10.1785/0120250139
Rossi, Y. Guéguen Ph, and 6 others. On the Use of 6c Seismic Station for Bending-to-Shear and Torsional Building Response Assessment. Available at SSRN: dx.doi.org/10.2139/ssrn.5220001
Celorio, M., Guéguen, Touma R., Roux P. 2026. Experimental characterization of urban-like scattering and attenuation from a dense nodal array: implications for seismic ground motion, accepted in GJI.
Research Progress and Future Directions
Our research has yielded three primary breakthroughs in seismic modeling and signal analysis, advancing our understanding of crustal dynamics and urban seismic response.
WP1: Initial Stress Computation
Developed a methodology for the effective computation of initial crustal stresses.
Enabled more accurate and realistic initialization of dynamic rupture scenarios.
WP2: Earthquake Signal Processing
Created advanced signal processing tools designed to extract both linear and nonlinear responses from seismic data.
Successfully applied these tools to characterize the nonlinear signatures of approximately 500 seismic stations across Japan.
WP3: Soil-City Interaction (SCI)
Conducted numerical modeling to quantify the damping effects produced by the interaction between the soil and urban environments (clusters of buildings).
Provided insights into how city configurations influence seismic energy dissipation.
Future Prospects: Advancing Damping Analysis
A critical challenge in geotechnical earthquake engineering remains the precise determination of damping from low to large strains.
Next Steps & Methodology:
Strain-Dependent Damping: Our upcoming phase focuses on bridging the gap in measuring how ground damping evolves as strain levels increase.
DAS Integration: We are currently leveraging Distributed Acoustic Sensing (DAS) technology. This allows for the high-resolution, direct measurement of strain rates.
Dynamic Property Mapping: By relating these strain rates to the dynamic properties of the underlying materials, we aim to develop a more robust model for site response and structural safety.
This project goes beyond the current seismic risk assessment practice, incorporating recent progresses made in earthquake data observation and numerical modelling. The key scientific questions are (1) how the spatial variability of the near-field seismic ground motion impacts the soil and the structure; (2) how the seismic excitations damage and change the medium properties; and (3) how the building clusters contribute to the spatial variability of the ground motion in urban environment. We study the 2016 Kumamoto in Japan and the 2019 Ridgecrest in California earthquakes. These events have a large number of records in the vicinity of the epicentral area. We then target the impact of a building environment on the seismic risk assessment of the city of Quito, Ecuador, located on a piggyback basin created on the hanging wall of an active reverse fault. Our project respond to the needs of low-probability-high-consequences (LPHC) seismic risk in urban areas subjected to nearby earthquakes.
Project coordination
Luis Fabian Bonilla (Département Géotechnique, environnement, risques naturels et sciences de la terre)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partnership
UNIV. Gustave Eiffel - GERS Département Géotechnique, environnement, risques naturels et sciences de la terre
ISTERRE Institut des Sciences de la Terre
BRGM BUREAU DE RECHERCHE GEOLOGIQUE ET MINIERE
Help of the ANR 360,870 euros
Beginning and duration of the scientific project:
- 48 Months
