More Like this

1. Scaling limits of branching Loewner evolutions and the Dyson superprocess

   https://doi.org/10.2140/pjm.2025.338.87  

   Healey, Vivian Olsiewski; Menon, Govind (January 2025, Pacific Journal of Mathematics)

   This work introduces a construction of conformal processes that combines the theory of branching processes with chordal Loewner evolution. The main novelty lies in the choice of driving measure for the Loewner evolution: given a finite genealogical tree T , we choose a driving measure for the Loewner evolution that is supported on a system of particles that evolves by Dyson Brownian motion at inverse temperature β ∈ (0,∞] between birth and death events. When β =∞, the driving measure degenerates to a system of particles that evolves through Coulombic repulsion between branching events. In this limit, the following graph embedding theorem is established: When T is equipped with a prescribed set of angles, {θv ∈ (0, π/2)}v∈T the hull of the Loewner evolution is an embedding of T into the upper half-plane with trivalent edges that meet at angles (2θv, 2π −4θv, 2θv) at the image of each vertex v. We also study the scaling limit when β ∈ (0,∞] is fixed and T is a binary Galton–Watson process that converges to a continuous state branching process. We treat both the unconditioned case (when the Galton–Watson process converges to the Feller diffusion) and the conditioned case (when the Galton–Watson tree converges to the continuum random tree). In each case, we characterize the scaling limit of the driving measure as a superprocess. In the unconditioned case, the scaling limit is the free probability analog of the Dawson–Watanabe superprocess that we term the Dyson superprocess. 

   more » « less
2. Localization and coalescence of seismicity before large earthquakes

   https://doi.org/10.1093/gji/ggaa315  

   Ben-Zion, Yehuda; Zaliapin, Ilya (October 2020, Geophysical Journal International)

   null (Ed.)

   SUMMARY We examine localization processes of low magnitude seismicity in relation to the occurrence of large earthquakes using three complementary analyses: (i) estimated production of rock damage by background events, (ii) evolving occupied fractional area of background seismicity and (iii) progressive coalescence of individual earthquakes into clusters. The different techniques provide information on different time scales and on the spatial extent of weakened damaged regions. Techniques (i) and (ii) use declustered catalogues to avoid the occasional strong fluctuations associated with aftershock sequences, while technique (iii) examines developing clusters in entire catalogue data. We analyse primarily earthquakes around large faults that are locked in the interseismic periods, and examine also as a contrasting example seismicity from the creeping Parkfield section of the San Andreas fault. Results of analysis (i) show that the M > 7 Landers 1992, Hector Mine 1999, El Mayor-Cucapah 2010 and Ridgecrest 2019 main shocks in Southern and Baja California were preceded in the previous decades by generation of rock damage around the eventual rupture zones. Analysis (ii) reveals localization (reduced fractional area) 2–3 yr before these main shocks and before the M > 7 Düzce 1999 earthquake in Turkey. Results with technique (iii) indicate that individual events tend to coalesce rapidly to clusters in the final 1–2 yr before the main shocks. Corresponding analyses of data from the Parkfield region show opposite delocalization patterns and decreasing clustering before the 2004 M6 earthquake. Continuing studies with these techniques, combined with analysis of geodetic data and insights from laboratory experiments and model simulations, might improve the ability to track preparation processes leading to large earthquakes. 

   more » « less
3. High-Precision Earthquake Catalog for Minto Flats Fault Zone, Central Alaska, Reveals Complex and Conjugate Faulting

   https://doi.org/10.1785/0120250177  

   Sims, Nealey E; Tape, Carl; Ruppert, Natalia A; West, Michael E (November 2025, Bulletin of the Seismological Society of America)

   The Minto Flats fault zone (MFFZ) in central Alaska is a left-lateral strike-slip fault system situated between the continental-scale right-lateral Denali and Kaltag-Tintina faults. The MFFZ has the potential to generate magnitude 7 earthquakes, and it hosted a magnitude 6 earthquake in 1995. It has also produced exotic events, such as very-low-frequency earthquakes and nucleation signals. We use network-matched filtering and relative earthquake relocation techniques to derive a detailed catalog of earthquake locations for the MFFZ. The catalog spans from August 2014 to December 2019, a time period including 13 temporary seismic stations in the region. Our results provide the most complete catalog for the MFFZ and include deeper events, clusters of shallow seismicity, and a complex and segmented fault structure not observed in the original regional catalog. We document right-lateral strike-slip faulting, conjugate to the main northeast-striking left-lateral faults of the MFFZ. Below Nenana basin, the relocated seismicity reveals northwest-dipping left-lateral faults, supporting the inference that deep crustal active faulting is associated with recent basin deformation. 

   more » « less
4. Characterizing differences in seismicity clustering and background rates between Hawaii and California

   https://doi.org/10.1093/gji/ggag341  

   Rinty, Sadia Marium; Goebel, Thomas_H W (August 2026, Geophysical Journal International)

   Summary The statistics of earthquake populations are governed by stress changes and event interactions at various scales which promote non-linear event cascades and seismicity clustering. Earthquake clustering in space and time is observed in both tectonic and volcanically dominated regions; however, notable differences exist for instance during eruptive sequences. Here, we characterize seismicity statistics in California and Hawaii and quantify differences in background rates and clustering. We compare three statistical approaches, i.e, i) Reasenberg declustering, ii) Gamma distribution fit, and iii) Nearest Neighbor Clustering which are applied to seismicity in Hawaii, southern California, and ETAS catalogs with known clustering characteristics. Tests with ETAS-catalogs suggest that background rate variations are more consistently resolvable using the Nearest Neighbor and Gamma distribution algorithm without requiring parameter adjustments to the specific study area. The Nearest Neighbor method tends to overestimate background rates, whereas the Gamma distribution algorithm shows systematic underestimation, suggesting that an ensemble model can improve the performance over any single method. Uncertainties in background rate estimates based on small magnitude events (e.g., M≥2.5) are high, in particular for the Reasenberg method, which overpredicts true rates by up to a factor of 4, and extrapolations to larger magnitudes need to be treated cautiously. Our analysis shows that the combination of the three approaches generates new insights into the processes that govern seismicity clustering. The analysis of southern California seismicity produces consistent results between the different methods, and the distribution of background seismicity rates is indistinguishable from Poissonian rates at magnitudes above 3.5. Conversely, the seismicity in Hawaii exhibits notable non-Poissonian background rate changes. Results from the Nearest Neighbor clustering analysis suggest notable differences between tectonic and volcano seismicity, including background rate changes and more pronounced spatiotemporal clustering around active volcanoes. Hawaiian seismicity is characterized by more localized spatial-temporal clustering, in particular during the 2018 eruption. This difference may be a result of magmatic, hydrothermal and eruptive processes, which make volcanic areas susceptible to stress perturbations and earthquake triggering at small scales. 

   more » « less
5. Potency–Magnitude Scaling Relations and a Unified Earthquake Catalog for the Western United States

   https://doi.org/10.1785/0320240022  

   Trugman, Daniel T; Ben-Zion, Yehuda (July 2024, The Seismic Record)

   Abstract Quantifying the size of earthquakes is a foundational task in seismology, and over the years several magnitude scales have been developed. Of these, only scales based on seismic moment or potency can properly characterize changes in event size without saturation. Here, we develop empirical potency–magnitude scaling relations for earthquakes in the western United States, allowing us to translate instrumental magnitude estimates into uniform measures of earthquake size. We use synthetic waveforms to validate the observed scaling relations and to provide additional insight into the differences between instrumental and physics-based magnitude scales. Each earthquake in our catalog is assigned a clustering designation distinguishing mainshocks from triggered seismicity, along with a potency-based magnitude estimate that is comparable to moment magnitude and that can be easily converted into other magnitude scales as needed. The developed catalog and associated scaling relations have broad applications for fundamental and applied studies of earthquake processes and hazards. 

   more » « less