More Like this

1. SWOT Satellite Altimetry Observations and Source Model for the Tsunami from the 2025 M  8.8 Kamchatka Earthquake

   https://doi.org/10.1785/0320250037  

   Ruiz-Angulo, Angel; Melgar, Diego; de_Marez, Charly; Deniau, Aurélien; Nencioli, Francesco; Hjörleifsdóttir, Vala (October 2025, The Seismic Record)

   On 29 July 2025, an Mw 8.8 earthquake struck off Kamchatka, Russia, generating a Pacific-wide tsunami and marking the largest earthquake since the launch of the surface water and ocean topography (SWOT) satellite in 2022. We analyze tsunami observations from SWOT together with three nearby deep-ocean assessment and reporting of tsunamis (DART) buoys to resolve the source of the event. SWOT provided the first high-resolution spaceborne track of a great subduction-zone tsunami, capturing waveforms that reveal complex propagation, dispersion, and scattering. Inversion of the DART time series using Gaussian unit sources shows that the rupture extended ∼400 km along strike, with peak uplift of ∼4 m, significantly different from the published finite-fault model. A blended source that combines the DART-inverted uplift with subsidence from the seismic–geodetic model best matches both datasets and reproduces the SWOT observations. Comparison with reconstructions of the 1952 Mw 9.0 Kamchatka earthquake indicates that the 2025 rupture likely reactivated significant portions of the megathrust that broke in 1952 but occurred farther down-dip and with little to no near-trench slip, consistent with its smaller tsunami impact. These findings highlight the hazard implications of short recurrence intervals of great earthquakes and show how rupture style governs tsunami severity. They also demonstrate the value of satellite altimetry for improving tsunami source characterization, post-event forecasting, and understanding of hydrodynamic processes. 

   more » « less
2. Using a dynamic earthquake simulator to explore tsunami earthquake generation

   https://doi.org/10.1093/gji/ggab470  

   Meng, Qingjun; Duan, Benchun; Luo, Bin (December 2021, Geophysical Journal International)

   SUMMARY Observations of historical tsunami earthquakes reveal that ruptures of these earthquakes propagate slowly at shallow depth with longer duration, depletion in high-frequency radiation and larger discrepancy of Mw–Ms than ordinary megathrust earthquakes. They can effectively generate tsunami and lead to huge damage to regional populated areas near the coast. In this study, we use a recently developed dynamic earthquake simulator to explore tsunami earthquake generation from a physics-based modelling point of view. We build a shallow-dipping subduction zone model in which locally locked, unstable patches (asperities) are distributed on a conditionally stable subduction interface at shallow depth. The dynamic earthquake simulator captures both quasi-static and dynamic processes of earthquake cycles. We find that earthquakes can nucleate on these asperities and propagate into the surrounding conditionally stable zone at slow speeds, generating tsunami earthquakes. A high normal stress asperity, representing a subducted seamount, can act as an asperity in some events but as a barrier in other events over multiple earthquake cycles. Low normal stress asperities typically act as asperities in tsunami earthquakes. The degree of velocity-weakening in the conditionally stable zone, which may sustain rupture at different speeds or stop rupture, is critical for tsunami earthquake generation and affects its recurrence interval. Distributed asperities may rupture in isolated events separated by tens of years, or in a sequence of events separated by hours to days, or in one large event in a cascade fashion, demonstrating complex interactions among them. The recurrence interval on a high normal stress asperity is much larger than that on low normal stress asperities. These modelling results shed lights on the observations from historical tsunami earthquakes, including the 1994 and 2006 Java tsunami earthquakes and 2010 Mentawai tsunami earthquake. 

   more » « less
3. Updated concepts of seismic gaps and asperities to assess great earthquake hazard along South America

   https://doi.org/10.1073/pnas.2216843119  

   Lay, Thorne; Nishenko, Stuart P. (December 2022, Proceedings of the National Academy of Sciences)

   So far in this century, six very large–magnitude earthquakes ( M W ≥ 7.8) have ruptured separate portions of the subduction zone plate boundary of western South America along Ecuador, Peru, and Chile. Each source region had last experienced a very large earthquake from 74 to 261 y earlier. This history led to their designation in advance as seismic gaps with potential to host future large earthquakes. Deployments of geodetic and seismic monitoring instruments in several of the seismic gaps enhanced resolution of the subsequent faulting processes, revealing preevent patterns of geodetic slip deficit accumulation and heterogeneous coseismic slip on the megathrust fault. Localized regions of large slip, or asperities, appear to have influenced variability in how each source region ruptured relative to prior events, as repeated ruptures have had similar, but not identical slip distributions. We consider updated perspectives of seismic gaps, asperities, and geodetic locking to assess current very large earthquake hazard along the South American subduction zone, noting regions of particular concern in northern Ecuador and Colombia (1958/1906 rupture zone), southeastern Peru (southeasternmost 1868 rupture zone), north Chile (1877 rupture zone), and north-central Chile (1922 rupture zone) that have large geodetic slip deficit measurements and long intervals (from 64 to 154 y) since prior large events have struck those regions. Expanded geophysical measurements onshore and offshore in these seismic gaps may provide critical information about the strain cycle and fault stress buildup late in the seismic cycle in advance of the future great earthquakes that will eventually strike each region. 

   more » « less
4. Long-Period Ground Motions from Past and Virtual Megathrust Earthquakes along the Nankai Trough, Japan

   Viens, L. (April 2019, Bulletin of the Seismological Society of America)

   Long‐period ground motions from large (Mw≥7.0) subduction‐zone earthquakes are a real threat for large‐scale human‐made structures. The Nankai subduction zone, Japan, is expected to host a major megathrust earthquake in the near future and has therefore been instrumented with offshore and onshore permanent seismic networks. We use the ambient seismic field continuously recorded at these stations to simulate the long‐period (4–10 s) ground motions from past and future potential offshore earthquakes. First, we compute impulse response functions (IRFs) between an ocean‐bottom seismometer of the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) network, which is located offshore on the accretionary wedge, and 60 onshore Hi‐net stations using seismic interferometry by deconvolution. As this technique only preserves the relative amplitude information of the IRFs, we use a moderate Mw 5.5 event to calibrate the amplitudes to absolute levels. After calibration, the IRFs are used together with a uniform stress‐drop source model to simulate the long‐period ground motions of the 2004 Mw 7.2 intraplate earthquake. For both events, the residuals of the 5\\% damped spectral acceleration (SA) computed from the horizontal and vertical components of the observed and simulated waveforms exhibit almost no bias and acceptable uncertainties. We also compare the observed SA values of the Mw 7.2 event to those from the subduction‐zone BC Hydro ground‐motion model (GMM) and find that our simulations perform better than the model. Finally, we simulate the long‐period ground motions of a hypothetical Mw 8.0 subduction earthquake that could occur along the Nankai trough. For this event, our simulations generally exhibit stronger long‐period ground motions than those predicted by the BC Hydro GMM. This study suggests that the ambient seismic field recorded by the ever‐increasing number of ocean‐bottom seismometers can be used to simulate the long‐period ground motions from large megathrust earthquakes. 

   more » « less
5. Coseismic Slip Model of the 19 September 2022 Mw 7.6 Michoacán, Mexico, Earthquake: A Quasi-Repeat of the 1973 Mw 7.6 Rupture

   https://doi.org/10.1785/0320220042  

   Liu, Chengli; Lay, Thorne; Bai, Yefei; He, Ping; Xiong, Xiong (April 2023, The Seismic Record)

   Abstract On 19 September 2022, a major earthquake struck the northwestern Michoacán segment along the Mexican subduction zone. A slip model is obtained that satisfactorily explains geodetic, teleseismic, and tsunami observations of the 2022 event. The preferred model has a compact large-slip patch that extends up-dip and northwestward from the hypocenter and directly overlaps a 1973 Mw 7.6 rupture. Slip is concentrated offshore and below the coast at depths from 10 to 30 km with a peak value of ∼2.9 m, and there is no detected coseismic slip near the trench. The total seismic moment is 3.1×1020  N·m (Mw 7.6), 72% of which is concentrated in the first 30 s. Most aftershocks are distributed in an up-dip area of the mainshock that has small coseismic slip, suggesting near-complete strain release in the large-slip patch. Teleseismic P waveforms of the 2022 and 1973 earthquakes are similar in duration and complexity with high cross-correlation coefficients of 0.68–0.98 for long P to PP signal time windows, indicating that the 2022 earthquake is a quasi-repeat of the 1973 earthquake, possibly indicating persistent frictional properties. Both the events produced more complex P waveforms than comparable size events along Guerrero and Oaxaca, reflecting differences in patchy locking of the Mexican megathrust. 

   more » « less