John Clinton

Improving our understanding of induced and natural earthquakes benefits from controlled experiments in insitu laboratories. To investigate the processes during an Mw∼0 earthquake, we performed the “ Mzero ” experiments in a densely instrumented testbed of the Bedretto Underground Laboratory. These multi‐day hydraulic stimulation experiments went the opposite direction to typical induced seismicity research in that they were designed to enhance seismic rupture. In the first experiment, MzeroA, the rock mass was preconditioned by injecting water for 4 days at a pressure just below fracture reactivation pressure followed by a hydraulic stimulation above reactivation pressure. This strategy aimed at increasing the fractures area near critical stress conditions for shear failure, thus facilitating larger ruptures. During MzeroA, an event with Mw–0.54 was induced, followed by a distinct aftershock sequence. This event was one magnitude unit larger than any preceding event. In the second experiment, MzeroB, stimulation was initiated directly, without preconditioning. Compared to MzeroA, MzeroB exhibited higher seismicity rates, a larger seismicity cloud, and a pronounced migrating seismicity front. Combining seismological and hydromechanical observations, we discuss mechanisms that may have influenced the contrasting seismicity responses. In addition to fluid preconditiong, stress transfer from the Mw–0.54 mainshock, and natural seasonal pressure changes, may have contributed to modulating the seismogenic response. However, the relative importance of these processes remains uncertain given experimental limitations. Our results highlight both the potential and challenge of designing hydraulic stimulations to enhance or suppress seismic rupture, with implications for earthquake physics and induced seismicity.

Earthquake early warning (EEW) systems that deliver real-time alerts to the public are now operating in Guatemala, El Salvador, Nicaragua, and Costa Rica. An independent system is operated by national seismological agencies in each country. The EEW systems were developed through the Alerta Temprana de Terremotos en América Central (ATTAC) project, a multi-year collaboration (2016–2024) led by ETH Zurich and funded by the Swiss Development Agency. These landmark systems are unique as they provide operational EEW in several low- and middle-income countries. Each system uses the same ETHZ-SED SeisComP EEW software that implements the virtual seismologist (VS) and finite-fault rupture detector (FinDer) algorithms. The national seismic monitoring infrastructures are supported by 72 EEW-ready strong-motion stations. Public alerts are disseminated primarily via a mobile application that has over one million users. EEW performance is regionally consistent due to shared real-time seismic data and common system architecture. Our evaluation period started when the software was installed and included periods of network and software optimization. The VS algorithm achieved an overall accuracy of 89%. Including FinDer reduced accuracy to 77%, mainly due to false positives in Nicaragua and Costa Rica that occurred early in the evaluation window. First alerts are generally available 10 s after origin time for shallow onshore events, with location and magnitude errors typically below 30 km and 0.5 units, respectively. Mobile alerting has proven effective in providing low-latency alerts to increasingly large numbers of users, with most users receiving red alerts within 2–8 s after issuance, though some variability can occur. Maintaining and enhancing EEW in the region requires sustained investment in seismic infrastructure, trained personnel, and dissemination solutions that, for the short term at least, will include the mobile application. Long-term viability depends on stable governance, consistent funding, and strengthened and coordinated public guidance on how to respond to alerts.

The Increasing Earthquake Awareness in Switzerland project set out to connect students, teachers, and the wider public with earthquake science by reviving and extending the nationwide seismo@school initiative. Supported by the Swiss National Science Foundation (SNSF) AGORA programme, the project developed a suite of multilingual teaching resources, deployed near real-time seismic sensors in schools, and created hands-on activities such as the Lambda Slinky Seismometer kit to engage 12- to 18-year-olds. Although Switzerland is exposed to only moderate seismic hazard, earthquakes remain the natural hazard with the highest damage potential. Because most residents have never experienced a damaging earthquake, educational programmes play a crucial role in raising awareness and strengthening preparedness. Moreover, seismo@school initiatives can inspire younger generations to pursue geosciences by helping them appreciate the relevance of the field. This article presents the rationale, implementation, and impact of the project, and may serve as a guide for other countries seeking to develop similar initiatives. It examines how experiential, data-driven educational approaches can improve earthquake awareness and preparedness in moderate-hazard regions, how school-based seismometers benefit both teaching and scientific monitoring while considering the practical challenges of installation and operation, and what institutional and policy conditions are required to sustain such efforts over the long term.

The Increasing Earthquake Awareness in Switzerland project set out to connect students, teachers, and the wider public with earthquake science by reviving and extending the nationwide seismo@school initiative. Supported by the Swiss National Science Foundation (SNSF) AGORA programme, the project developed a suite of multilingual teaching resources, deployed near real-time seismic sensors in schools, and created hands-on activities to foster engagement of 12 to 18-year-olds. Although Switzerland is exposed to only moderate seismic hazard, earthquakes remain the natural hazard with the highest potential impact. Because most residents have never experienced a damaging earthquake, educational programmes play a crucial role in raising awareness and strengthening preparedness. Moreover, seismo@school initiatives can inspire younger generations to pursue geosciences by helping them appreciate the relevance of the field. This article presents the rationale, implementation, and impact of the project, and may serve as a guide for other countries seeking to develop similar initiatives. It examines how experiential, data-driven educational approaches can improve earthquake awareness and preparedness in moderate-hazard regions, how school-based seismometers benefit both teaching and scientific monitoring while considering the practical challenges of installation and operation, and what institutional and policy conditions are required to sustain such efforts over the long term.

Distributed Acoustic Sensing (DAS) enables the acquisition of seismic data with unrivalled spatio-temporal resolution over very large distances. Railway fiber-optic networks, originally deployed for telecommunications, offer cost-effective opportunities to monitor and characterize the subsurface at multiple scales. Here, we present a project conducted with the Swiss Federal Railways (SBB) involving the interrogation of dark fibers running along two perpendicular railway tracks, each approximately 40 km long. Data were acquired over three months using a dual-channel Sintela Onyx interrogator, with variable acquisition setups (spatial sampling, gauge length, and sampling frequency) tailored to different scientific objectives described below.The primary objective was to assess the feasibility of using pre-existing telecommunications fibers for structural track-bed monitoring, specifically shallow subsurface Vs characterization through inversion of Rayleigh-wave dispersion curves (MASW). This requires high spatial sampling and short gauge length (3 m and 6 m, respectively) to capture short wavelengths. Several ambient noise interferometry strategies were tested, including stacking (1) all available time windows with various preprocessing schemes, (2) only time windows exhibiting strong directional wavefields, and (3) a coherent-source subsampling approach based on a Symmetric Variational Autoencoder to identify time windows contributing the most useful seismic energy. Unsurprisingly, trains constitute the most energetic and reliable seismic sources, from which dense Vs profiles can be derived, demonstrating the effectiveness of both the processing and inversion workflows.Beyond shallow characterization, the experiment also yielded valuable data to complement dense nodal arrays deployed near Lavey-les-Bains, a site of significant geothermal interest and complex geological structure. The main objectives in this context are to (1) help characterizing the subsurface over the first kilometers, (2) investigate its relationship to geothermal circulation, (3) evaluate the joint use of dense nodal and DAS data for imaging, and (4) establish a high-quality, open-access dataset to support the development of next-generation passive imaging methodologies.Finally, at an even larger scale, the experiment provided the opportunity to explore how DAS data can be leveraged within the operational Swiss Seismological Service (SED) network and to assess whether DAS can augment standard seismicity catalogues. Lower-resolution data (100 m spatial sampling, 200 Hz sampling frequency) were streamed and converted in real time into standard seismic formats (miniSEED and StationXML), demonstrating the feasibility of integrating DAS data into SeisComP for both automatic and manual processing.We will present the dataset along with key results relevant to the three purposes outlined above.We acknowledge Allianz Fahrbahn (grant agreement No. 100 072 202) for enabling this study.

We present an updated and extended seismotectonic earthquake catalog of Switzerland and surrounding regions. This SECOS25 catalog serves as input for the seismic-source component of Switzerland’s next generation seismic hazard model to be developed by the Swiss Seismological Service (SED) over the coming years. The SECOS25 catalog includes 51 years of instrumental seismicity detected and located by the SED between 1975 and 2025. For the digital era of the SED catalog (phase picks and seismograms available in digital form) starting in 1984, hypocenters were consistently relocated in absolute terms using a recent 3D P and S-wave crustal velocity model. Starting from these improved hypocenters, double-difference relative relocations were performed at different scales (local clusters as well as regional scales), combining differential times from manual picks and waveform cross correlations. A merging procedure was developed that selects the preferred location method (bulletin location, absolute relocation, relative relocation) based on location-quality criteria for each hypocenter. The proposed procedure provides various hypocenter uncertainty measures and ensures the maximum possible hypocenter-location accuracy and precision for each event. Local magnitudes were revised using a new set of consistent amplitude measurements (doi.org/10.1785/0120250032) and a new magnitude model. For each earthquake, we provide moment magnitudes from native methods if available (either from moment tensors or spectral fitting) or revised scaling relationships. Finally, we link the hypocenters with catalogs of moment tensors (containing about 80 solutions) as well as first-motion focal mechanisms (containing about 600 solutions).The SECOS25 catalog serves as a base for further down-stream seismotectonic components of the seismic-source model. This includes heat maps of seismic activity and moment release across Switzerland as well as maps of deformation regimes and stress orientations derived from the analysis and inversion of focal mechanisms. Finally, we apply an enhanced version of the HyFi method (doi.org/10.1029/2023JB026352) to the SECOS25 catalog to systematically identify previously unknown seismically active fault segments and their orientations. The derived information will contribute to a refined definition of seismic zonation as well as faulting styles and preferred rupture orientations required for hazard computations. The SECOS25 catalog and derived products therefore also contribute to an improved understanding of present-day seismotectonic processes in the Central Alpine region.

We present new local magnitude models for Switzerland, derived using a top-quality input dataset of ground-motion intensity measures, obtained through an automated and consistent waveform processing workflow (https://doi.org/10.1785/0120250032). The input dataset includes Wood-Anderson displacement response amplitudes calculated from 150,000 waveforms generated by about 15,000 earthquakes in the region of interest. This dataset is substantially larger than those used in previous magnitude studies in Switzerland and contains a large number of recordings at short distances for smaller events (about 5,000 earthquakes with magnitudes lower than 1, and about 1500 records at hypocentral distances shorter than 5 km), which were sparse in earlier studies. The parametrization of the local magnitude model is based on a detailed investigation of attenuation characteristics of the Wood-Anderson response amplitudes, comprising: (i) linear and logarithmic distance terms to represent different physical mechanisms of seismic wave propagation; (ii) hinge distances to allow modelling the effects of Moho reflections and the associated changes in attenuation rate; (iii) regional adjustments (Swiss Alps vs Swiss northern Foreland) based on the length and location of the surface projection of the source-to-site ray paths. Model coefficients are determined through mixed-effects regressions, thus allowing the derivation of station-magnitude correction terms consistent with the reference rock-like ground type used for mapping seismic hazard in Switzerland. We assess and validate the model’s performance via uncertainty analyses, validation against recent data not used in model calibration, validation against recordings of major Swiss events, and comparisons with results obtained from alternative, fully independent modelling approaches (including non-parametric and 2D cell-based methods). The new model yields systematically lower magnitudes, with an average difference of 0.1-0.2 magnitude units for smaller events with magnitudes below 2.5 and for earthquakes located in the Swiss northern Foreland, compared to the currently authoritative catalogue magnitudes. Based on the new candidate magnitude model, we present and discuss an updated empirical scaling relationship between local and moment magnitudes.

The Bedretto Underground Laboratory for Geosciences and Geoenergies (BULGG, ETH Zurich) operates a dense, multi-scale seismic monitoring framework for on-fault observation of induced seismicity during underground stimulation experiments. The system integrates permanent seismic stations (500 to 10k samples per second, sps), high-rate experimental deployments (up to 200k sps), and distributed acoustic sensing (DAS; up to 4000 sps), providing high spatial and temporal data coverage at the reservoir and local scale. This contribution documents real-time seismic monitoring during underground experiments and the generation of associated post-processed earthquake catalogues.The combined instrumentation is used for monitoring of hydraulic stimulation and geothermal project experiments, including the Fault Activation and Earthquake Rupture (FEAR) ERC project and Geothermal Test-Bed (GTB) activities. Permanent monitoring provides manually reviewed earthquake locations and magnitudes in a continuous reference earthquake catalogue, continuously updated since 2021. Experimental deployments enable near real-time event detection, characterization, and Traffic Light System (TLS) alerting, including borehole DAS observations since 2024.For the FEAR and GTB experiments, additional post-processed catalogues provide optimal yet conventional event parameters based on the final instrumentation configuration, optimized phase picking and hypocenter locations. The resulting catalogues provide consistent absolute locations and high-resolution double-difference relocations based on fully repicked waveform data.Event magnitudes are estimated using multiple complementary approaches. The backbone national network provides a Swiss-specific local magnitude (Mlhc) using station corrections, while the permanent BedrettoLab network applies conventional local magnitude (MLc) from Wood–Anderson amplitudes. Experimental catalogues include relative moment magnitudes derived from acoustic emission amplitude ratios (MwA) calibrated against collocated accelerometers. Ongoing developments include spectral moment magnitudes and DAS strain-rate-based magnitude estimates to improve characterization of small-magnitude events.The BedrettoLab monitoring framework, implemented in SeisComP, addresses challenges such as electromagnetic noise, tunnel operations, and heterogeneous sensor coverage while ensuring continuous acquisition, archiving, and FDSN-compliant data access. Beyond Bedretto, this on-fault, densely instrumented approach demonstrates how integrated DAS, permanent, and experimental monitoring can substantially improve event detection, location accuracy, and magnitude estimation, providing a transferable framework for induced seismicity monitoring, operational decision-making, and risk mitigation in geothermal and underground engineering applications.