Geophysical Research Letters最新文献

We deployed 30 temporary seismic stations around the source region of the 2024 M_w 7.5 Noto Peninsula earthquake to investigate the relationship between mainshock rupture and fault geometry. Using machine learning techniques, we detected and precisely located 46,252 aftershocks, revealing several fault planes corresponding to active faults ruptured during the mainshock. Two subparallel landward-dipping planar structures were identified near the mainshock hypocenter, converging westward to the Wajima-Oki segment. This geometry suggests that complex rupture episodes near the hypocenter resulted from successive ruptures on adjacent fault planes rather than slip on a single plane. At the western edge of the 2024 rupture area, aftershocks extend close to but rarely occur on the fault that ruptured during the 2007 M_w 6.7 earthquake, suggesting that the 2024 earthquake did not re-rupture the same faults of the 2007 earthquake.

Springtime warming over Northern Mid-High-latitude Land profoundly affects plant life cycles and water resources, yet large model uncertainty limits climate risk assessment. Here, we develop a novel emergent constraint that targets the key uncertainty source—model divergence in surface-albedo feedback linked to historical snowmelt sensitivity. This approach halves the spread of projected warming and reveals a pronounced geographical asymmetry. Under the high-emission scenario (SSP5-8.5), current climate models underestimate end-of-century warming over Eurasia by 0.80°C but overestimate it over North America by 0.44°C. These refined projections substantially alter ecological outcomes: the start of the growing season is predicted to advance by about 18 days in Eurasia and 8 days in North America, representing a 3-day greater advance and 1-day delay compared with original estimates. Our findings offer a more reliable basis for assessing climate change impacts on ecosystems and water resources and highlight the urgency of region-specific adaptation strategies.

Quantifying how incident ocean waves transfer energy into seismic surface waves along the nearshore is essential for understanding coastal hazards and Earth–ocean coupling, yet time-resolved in situ estimates have been scarce. Here we use a beach-deployed distributed acoustic sensing array co-located with an ocean-bottom node to directly measure the conversion efficiency from wave impacts to Rayleigh-type ground motion at 4–12 Hz. Frequency–wavenumber analysis, beamforming, and local back-projection consistently locate sources along a fixed, wave-breaking coastal segment, while particle-motion ellipticity confirms the Rayleigh character. Calibrating distributed acoustic sensing strain to ground velocity and combining nearshore wave energetics yields an energy-conversion efficiency on the order of 10⁻⁶. The efficiency is strongly modulated by tide, with high-tide conditions enhancing coupling even though the source region remains stationary. Our results establish a quantitative benchmark for dynamic ocean-to-Earth energy transfer at the land–sea interface and provide a generalizable framework for coastal monitoring using existing fiber infrastructure.

While the isolated effects of solar flares on low-latitude ionospheric electrodynamics have been well documented, the coupled system response of the equatorial electrojet (EEJ), auroral electrojet (AEJ), field-aligned currents (FACs), and asymmetric ring current (ASY-H) remains poorly understood. This study statistically analyzes 1,657 X/M-class flares (2001–2017) to quantify rapid electrodynamic changes across current systems. Our results indicate (a) flare intensity-dependent enhancements in eastward EEJ, suppressed equatorial ionospheric vertical drift (V_z), and increased ASY-H; (b) negligible flare influence on AEJ; and (c) R2 FACs intensification in the dusk sector, linking ionospheric dynamics to asymmetric ring current perturbations. These observations reveal transient electrodynamic coupling within the geospace associated with flares, independent of solar wind forcing, advancing understanding of flare-driven ionosphere-magnetosphere interactions.

Hydroclimatic variations in mid-latitude Asia during the early to mid-Holocene and associated mechanisms remain disputed, hampering our understanding of atmospheric circulation controls on regional climatic changes. We report Holocene alkenone records from two Siberian lakes, documenting lake temperature and hydrological changes, and synthesize records from mid-latitude Asia to address regional hydroclimatic variability. Relatively dry conditions occurred in westerlies-dominated regions and extended to marginal monsoon regions before ∼6,000 a BP, followed by wetting transitions during ∼6,000–5,000 a BP, despite contrasting temperature variations between two regions. We suggest that early to mid-Holocene drought in mid-latitude Asian interior appears to be associated with enhanced anticyclonic system over mid-high latitude Eurasian continent, induced by prevailing cold airmasses, which extended its hydrological control to marginal monsoon regions. Our findings explain the spatial heterogeneity of hydrological changes in mid-latitude Asia, and opposite temperature-moisture associations within westerlies-dominated and marginal monsoon regions during the early to mid-Holocene.

Pleistocene cold periods created widespread periglacial conditions across mid-latitudes, but isolating their geomorphic impact from modern climate, tectonics, and rock strength is challenging. We studied Appalachian (Eastern U.S.) ridgelines across a paleoclimate gradient, controlling for bedrock and structure, to test if colder periglacial conditions led to flatter hilltops and longer hillslopes, features typical of permafrost landscapes. We find that hilltop curvature and hillslope length vary with paleotemperature, not modern climate or uplift. Despite gentler slopes, erosion rates near the Last Glacial Maximum ice margin are similar or higher than southern sites for resistant bedrock units, suggesting frost cracking and solifluction enhanced hilltop lowering and valley infilling. Hillslope morphometry patterns resemble landscapes responding to modern Arctic climate gradients, implying a long-lived geomorphic signature of permafrost-driven processes. This cold-climate legacy can remain imprinted in modern mid-latitude terrain, complicating efforts to link current climate with landscape form where erosion rates are slow.

Snow dampens sounds, but anecdotal reports concisely describe audible propagating collapse events—firnquakes—in Antarctic and Arctic snowfields. We propose combining granular and continuum mechanics to form a testable theory for conditioning, triggering, and propagation of firnquakes consistent with scarce data. A central condition for collapse events is unconsolidated firn at depth. As firn grains compact, stresses are transmitted along force chains which carry the overburden and transition into a continuous medium by pressure sintering. This granular legacy creates solid-like supports of denser layers that keep the material below unconsolidated. Dynamic amplification triggers local brittle failure of the supports, which induces a cascade of collapse propagation. Using bulk density from ice cores as proxy for stiffness, we find the flexural wave speed by collapsing supports matches the recorded firnquake velocities on the order of 100 m/s. Our theory is to be tested in firn sheets and other compacting granular materials.

Reconstructing oroclinal orogens along the Fuegian Andes-northern Antarctic Peninsula provides critical constraints on the pre-opening tectonic evolution of the Drake Passage, although such efforts are limited by a lack of reliable Cretaceous paleomagnetic and geochronological data. Here, we present new paleomagnetic, ⁴⁰Ar/³⁹Ar, and apatite U-Pb geochronological data to reconstruct the oroclinal bending of this belt. Our results reveal that oroclinal bending in the northern Antarctic Peninsula (∼67°–63°S) and the Fuegian Andes both occurred at ∼100–90 Ma, mainly driven by compression from the northward-moving Antarctic Peninsula and southeastward-moving Cordillera Darwin Metamorphic Complex. We propose that the orocline Drake Passage boundary primarily formed during this period. This oroclinal weak zone served as a fundamental prerequisite in opening the Drake Passage, facilitating the separation of the Fuegian Andes and Antarctic Peninsula.

Kinetic energy (KE) transfer between spatial scales contributes to the ocean's energy budget by linking scales of KE supply and KE dissipation. Numerical simulations have indicated that for scales smaller than the baroclinic deformation radius, cross-scale KE transfer has complex spatial and temporal variability, modulated by mixed layer properties, fronts, and eddies. Here, over a decade of upper-ocean surface velocity data, collected from high-frequency radar within the Santa Barbara Channel, are used to estimate cross-scale KE transfer. The transfer of KE across 7 km has strong seasonal and interannual variations linked to energy exchange with the atmosphere. This study observationally confirms (a) the importance of the surface divergence field in determining the direction of the KE transfer and (b) the equi-partitioning of KE transfer between divergent and straining motions. The temporal variability in KE transfer suggests that surface forcing influences the long-term redistribution of energy between scales.

At Mars, the MAVEN spacecraft has made observations of Hot Flow Anomalies (HFAs) in the foreshock. Due to the bow shock's proximity to the planet, it is theorized that HFAs contribute to atmospheric escape at Mars through the excavation of ionospheric ions. A case study investigates one HFA observation, with parameters suggesting a novel mechanism for planetary ion extraction. The event is further characterized by elevated number densities of $���O^{+}��$ and $���O_2^{+}��$ ions observed prior to the current sheet crossing. Statistical study is conducted on a set of 91 events, facilitating the estimation of HFA frequency at Mars to be 1/day. The estimated ion escape of the event is approximately 9$���\%��$ of the typical ion escape rate under nominal conditions at Mars. Calculation of further events reveals escape rates between 1 and 9$���\%��$ of the nominal conditions. This represents a modest contribution to the overall escape, highlighting a potentially underexplored pathway.