We present a dynamic rupture model of the 2016 M
7.8 Kaikōura earthquake to unravel the event's riddles in a physics-based manner and provide insight on the mechanical viability of competing ...hypotheses proposed to explain them. Our model reproduces key characteristics of the event and constraints puzzling features inferred from high-quality observations including a large gap separating surface rupture traces, the possibility of significant slip on the subduction interface, the non-rupture of the Hope fault, and slow apparent rupture speed. We show that the observed rupture cascade is dynamically consistent with regional stress estimates and a crustal fault network geometry inferred from seismic and geodetic data. We propose that the complex fault system operates at low apparent friction thanks to the combined effects of overpressurized fluids, low dynamic friction and stress concentrations induced by deep fault creep.
The basaltic caldera volcanoes in the Galápagos Islands characteristically erupt lavas via summit circumferential and radial flank dike intrusions, but the underlying magma plumbing systems remain ...enigmatic. Here, we document surface displacements of Wolf volcano using interferometric synthetic aperture radar (InSAR) data from 2015 to 2022. We show that Wolf volcano experienced 6‐years of continuous inflation after the 2015 eruption, followed by a shallow flank eruption in January 2022. The deformation is modeled with a vertical caldera ring‐fault and a radial dike on the southeast flank. The ring‐fault underwent opening and reverse faulting during the inflation period, and closure and normal faulting during and after the eruption. Stress interactions between the ring‐fault and the flank dike suggest the asymmetric opening of the ring‐fault promotes flank eruptions. The best‐fit deformation model differs from the previous models and offers an alternative view of how magma is fed into radial dikes during flank eruptions.
Plain Language Summary
The 2022 eruption at Wolf volcano in the Galápagos Islands started from a radial fissure on the SE flank, which was different from the 2015 eruption that mainly occurred inside the caldera. We track the sequence of ground deformation before, during and after the 2022 eruption using InSAR data. We find that Wolf volcano experienced continuous inflation before the 2022 eruption, followed by deflation during and after the eruption, resulting in complex ground deformation within and beyond the caldera and on the SE flank. We propose a model with ring fault slip and opening/closure to explain the observed ground deformation within the caldera. We find that opening and reverse slip of the ring fault can explain the inflation before the 2022 eruption, while closure and normal slip caused the deflation period during and after the eruption. The asymmetric opening of the ring fault changed the stresses in the volcano and promoted the occurrence of the flank eruption. Our model is different from the dike rotation model that was proposed for Fernandina volcano and may allow for improved forecasts of the location and style of future eruptions on the Galapagos Islands.
Key Points
Interferometric synthetic aperture radar data are used to study ground deformation before, during and after the 2022 Wolf eruption
A ring fault opening/closure model fits ground deformation of the caldera well
Asymmetric opening of the ring fault promotes flank eruptions at Wolf volcano
From 2009 to 2016, four earthquakes (Mw > 6) occurred in central Italy, which are the Apr. 6th, 2009 earthquake, Aug. 24th, 2016 earthquake, Oct. 26th, 2016 earthquake and Oct. 30th, 2016 earthquake. ...To investigate their seismic mechanism, triggering relationships and impacts on the surrounding areas, we obtained their coseismic deformation fields using the data of interferometric synthetic aperture radar (InSAR) and global positioning system (GPS). We constructed three variable-strike fault models for the four events which can be more consistent with the actual fault and improve the overall fitting precision. On this basis, we calculated the coseismic slips of the first two earthquakes respectively and obtained that of the last two earthquakes by a joint inversion method. Then the Coulomb stress changes of those four earthquakes were calculated. The results show that these earthquakes are mainly caused by normal faults that strike approximately NW-SE or NNW-SSE and dips to SW or WSW with angles between 33° and 47°. All these events are shallow earthquakes, and the main fault slips are located in the area with depth of 0–10 km, accompanied by some surface ruptures. The maximal slip with a value of 3.44 m at ~4 km depth was caused by the Oct. 30th, 2016 earthquake. The inverted magnitudes of the four earthquakes are Mw 6.26, Mw 6.20, Mw 6.19 and Mw 6.60. The stress changes indicate that the former earthquake accelerated the latter one successively. Moreover, there is a seismic gap between the regions of the Apr. 6th, 2009 and Aug. 24th, 2016 earthquakes and a high stress-accumulating area in the south of the Apr. 6th, 2009 earthquake region. So, the Montereale fault in the gap and the Barisciano fault located on the southeast of the Paganica fault might have great earthquake risks due to the massive accumulated stress.
•Coseismic deformation of the four earthquakes (Mw > 6) occurred in central Italy.•These earthquakes are caused by normal faults with some strike-slip component.•Stress changes indicate the former earthquake accelerated the latter one successively.•There is a seismic gap and a high stress-accumulating area may have earthquake risks.
The mechanisms of unusual shallow intraplate earthquakes that occasionally occur in stable cratons remain poorly understood. Here we analyze coseismic and postseismic displacement fields associated ...with the 2016 Petermann Ranges earthquake in central Australia using interferometric synthetic aperture radar data. The earthquake ruptured a previously unmapped fault and was dominated by thrust slip motion of up to 95 cm within the top 3 km of the crust. Postseismic deformation analysis suggests that a combination of poroelastic rebound and afterslip are responsible for the observed signals. The inferred afterslip overlapping spatially with the coseismic rupture highlights that the postseismic slip is coupled with the pore fluid flow around the fault zones. Analysis of historic groundwater‐level changes suggests that shallow seismicity around the Petermann Ranges may have been triggered by environmental stress perturbations due to the fluctuations of groundwater level; however, it is not easy to document statistical significance of this correlation.
Plain Language Summary
Shallow surface‐rupturing earthquakes have been observed globally. However, how these events are triggered and why they sometimes occur within stable continents is largely unknown. We carefully study the coseismic and postseismic deformation of a 2016 Mw 6 earthquake in central Australia to determine the source parameters and slip distributions. We find the coseismic slip and early afterslip are concentrated at depths shallower than 3 km, and poroelastic rebound substantially contributes to the early period of postseismic deformation. We further investigate potential mechanisms to explain rock failure at such shallow depth and find a possible relationship between the fluctuations of groundwater level and the occurrence of shallow seismicity in the region. The results of this study help shed light on the processes and causes of shallow earthquakes.
Key Points
Coseismic slip of the 2016 Mw 6 Petermann Ranges earthquake is concentrated at shallow depths between 0 and 3 km
Postseismic displacements are governed by a combination of poroelastic rebound and afterslip
The occurrence of shallow earthquakes might be caused by groundwater levels changes in central Australia
We derive the ALOS‐2 coseismic interferograms, pixel‐offsets and Sentinel‐2 sub‐pixel offsets of the 2023 Mw7.8 and Mw7.7 Kahramanmaras, Turkey earthquake sequence. Offset maps show that the sequence ...ruptured ∼300 km along the East Anatolian Fault (EAF) and ∼180 km along the secondary Cardak and Dogansehir faults. We infer the coseismic slip distribution and interseismic fault motion by inverting the co‐ and inter‐seismic observations. Inversion results show that the coseismic slip (∼8.0 m) and interseismic strike‐slip rate (∼4.6 mm/yr) on the main rupture of the Mw7.8 event are basically consistent with the ∼8.4 m and ∼3.9 mm/yr of the Mw7.7 event. Most coseismic slips of the Mw7.8 and Mw7.7 events occur within 10 and 12 km at depth, respectively, in keeping with the interseismic locking depth of 10.4 ± 3.3 km and 11.1 ± 3.1 km. This implies that the coseismic rupture kinematics correlate with the interseismic strain accumulation. Moreover, static stress changes show that the Mw7.7 event is likely promoted by ∼2 bar stress increase from the Mw7.8 event on the central section of its main rupture.
Plain Language Summary
The middle and northern sections of the East Anatolian Fault (EAF) have experienced seven major earthquakes (M > 6.0) since the twentieth century, in accordance with the fast slip rate (∼10.5 mm/yr) and shallow locking depth (∼5 km) (Bletery et al., 2020, https://doi.org/10.1029/2020gl087775), leaving a well‐known seismic gap, the Pazarcık segment in the southern section of the EAF. Stress analysis by Nalbant et al. (2002, https://doi.org/10.1016/s0012-821x(01)00592-1) suggested that this seismic gap has potential to produce an Mw ≥ 7.3 earthquake. The 2023 Mw7.8 and Mw7.7 Kahramanmaras, Turkey earthquake sequence ruptured the Pazarcık segment. This earthquake sequence offers a valuable opportunity to explore the critical stage of the seismic cycle from interseismic strain accumulation to coseismic rupture. We extract the surface fault traces from the deformation maps derived from the ALOS‐2 interferometric synthetic aperture radar (InSAR), pixel offset and Sentinel‐2 sub‐pixel offset measurements, and then construct a seven‐segment fault geometric model according to the fault segmentation based on Duman and Emre (2013, https://doi.org/10.1144/SP372.14). By inverting the coseismic interferograms and pixel offsets and the interseismic LOS velocities from Weiss et al. (2020, https://doi.org/10.1029/2020GL087376), we determine the coseismic slip model of Mw7.8 and Mw7.7 earthquakes, and relate it to the interseismic kinematics.
Key Points
We drive a complete series of coseismic deformation maps and detailed slip distribution of the 2023 Kahramanmaras earthquakes
The Mw7.7 event produced normal dip‐slip (∼6 m) near the Goksun releasing bend and thrust dip‐slip (∼2 m) on the Dogansehir fault
The coseismic slip behaviors on the Cardak and Pazarcık faults correlate with the interseismic kinematics
Abstract
The safe treatment of heavy metals in wastewater is directly related to human health and social development. In this paper, a new type of recyclable adsorbent is synthesized through the ...oxidation of enhancer and modification with magnetic nanoparticles. The new adsorbent not only inherits the advantages of multiwall carbon nanotubes (6O-MWCNTs), but also exhibits a new magnetic property and further improved adsorption capacity, which is conducive to the magnetic separation and recovery of heavy metals. The adsorption results indicate that multiwall magnetic carbon nanotubes (6O-MWCNTs@Fe
3
O
4
) have a good performance for Pb(II) selective adsorption, with a maximum adsorption capacity of 215.05 mg/g, much higher than the existing adsorption capacity of the same type of adsorbents. Under the action of an external magnetic field, 6O-MWCNTs@Fe
3
O
4
that adsorbed metal ions can quickly achieve good separation from the solution. The joint characterization results of FTIR and XPS show that under the action of both coordination and electrostatic attraction, the C=O bond in the –COOH group is induced to open by the metal ions and transforms into an ionic bond, and the metal ions are stably adsorbed on the surface of 6O-MWCNTs@Fe
3
O
4
. Pb(II) has a stronger attraction than Cu(II) and Cd(II) to the lone pair of electrons in oxygen atoms to form complexes, due to the covalent index of Pb (6.41) is more larger than that of Cu (2.98) and Cd (2.71).These data provide a new type of recyclable adsorbent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge.
Highlights
Stretchable MXene organohydrogel contains MXene network for electron conduction and water/glycerin binary solvent for ion transmission was prepared.
The MXene organohydrogel exhibits ...exceptionally enhanced EMI shielding performance compared to hydrogel, as well as low-temperature tolerance, anti-drying ability.
Conductive hydrogels have potential applications in shielding electromagnetic (EM) radiation interference in deformable and wearable electronic devices, but usually suffer from poor environmental stability and stretching-induced shielding performance degradation. Although organohydrogels can improve the environmental stability of materials, their development is at the expense of reducing electrical conductivity and thus weakening EM interference shielding ability. Here, a MXene organohydrogel is prepared which is composed of MXene network for electron conduction, binary solvent channels for ion conduction, and abundant solvent-polymer-MXene interfaces for EM wave scattering. This organohydrogel possesses excellent anti-drying ability, low-temperature tolerance, stretchability, shape adaptability, adhesion and rapid self-healing ability. Two effective strategies have been proposed to solve the problems of current organohydrogel shielding materials. By reasonably controlling the MXene content and the glycerol-water ratio in the gel, MXene organohydrogel can exhibit exceptionally enhanced EM interference shielding performances compared to MXene hydrogel due to the increased physical cross-linking density of the gel. Moreover, MXene organohydrogel shows attractive stretching-enhanced interference effectiveness, caused by the connection and parallel arrangement of MXene nanosheets. This well-designed MXene organohydrogel has potential applications in shielding EM interference in deformable and wearable electronic devices.
Extension deficit builds up over centuries at divergent plate boundaries and is recurrently removed during rifting events, accompanied by magma intrusions and transient metre-scale deformation. ...However, information on transient near-field deformation has rarely been captured, hindering progress in understanding rifting mechanisms and evolution. Here we show new evidence of oblique rift opening during a rifting event influenced by pre-existing fractures and two centuries of extension deficit accumulation. This event originated from the Bárðarbunga caldera and led to the largest basaltic eruption in Iceland in >200 years. The results show that the opening was initially accompanied by left-lateral shear that ceased with increasing opening. Our results imply that pre-existing fractures play a key role in controlling oblique rift opening at divergent plate boundaries.
SUMMARY
On 28 September 2018, a Mw 7.5 strike-slip earthquake occurred in Sulawesi Island, Indonesia, and it unexpectedly triggered a tsunami. To clearly understand the spatiotemporal evolution ...process of source rupture, we collected the far-field body wave data and utilized the back-projection method together with finite fault inversion method to investigate the rupture kinematics of this earthquake. Results obtained with the two methods have good consistency and complementarity. We hold that the rupture expanded from the epicentre and propagated bilaterally towards the north and south along the strike direction during the first 24 s, and then to the south. Therefore, the whole rupture process consists of two main stages. For the second stage, the fault segment experienced most of the moment release between 0 and 15 km depth, while the fault plane tended to slip at greater depth (down to 20 km) in the first stage. The total length of the rupture was about 200 km and the seismic moment was ∼2.48 × 1020 Nm, which was equivalent to Mw 7.5. The surface rupture was evident and the maximum slip of 6.24 m was observed in the Palu basin, which was close to Palu city. The rupture was dominated by left-lateral strike-slip with both normal and thrust components as well. The normal slip exhibited in the shallow part of the fault on the north side of Palu bay together with the special geographical location of Palu bay likely favored tsunami genesis.
As occurred during the tourist season, the 2017 Mw 6.5 Jiuzhaigou (China) earthquake led to destructive damages. The seismogenic fault of this event was merely speculated to be the northern extension ...of the Huya fault, while no apparent surface ruptures were discovered in the field investigation. Previous studies and released moment tensor solutions indicated the Jiuzhaigou earthquake was dominated by left-lateral strike slip with partial normal-slip component. It seems unintelligible that the normal slip occurred in this event as the epicenter was located near the boundary of convergent blocks. Hence, a reasonable and elaborate source rupture model is necessary to investigate such a blind fault and the role it plays in the complex fault system of this region. Combining space-based geodetic, teleseismic or regional seismic observations can provide detailed information about earthquake ruptures. We first attempted to determine the fault geometry using the Bayesian approach with synthetic aperture radar interferograms (InSAR). And then the fault geometry was refined based on the relocated aftershock distribution, and a two-segment fault model was constructed. Based on the two-segment model, we resolved the source rupture process of the 2017 Jiuzhaigou earthquake through the joint inversion of strong-motion, teleseismic body-wave and InSAR data. The inversion results reveal a hybrid source mechanism, in which normal and thrust slips coexist besides the strike-slip component. We suggest that the eastward motion with the extrusion of the lower crustal flow in the northeastern margin of the Bayan Har block is responsible for such a faulting behavior. The co-seismic Coulomb stress changes show a significant stress loading in the western segment of the Tazang fault, increasing its seismic hazard. Due to the lack of aftershocks to the southeast of the seismogenic fault, the probably enhanced seismicity in the northern segment of the Huya fault is also worth further attention.
•A two-segment fault geometry delineated by the relocated aftershock distribution.•A joint inversion combining seismological and geodetic data.•A hybrid source mechanism in which normal and thrust slips coexist.•The extrusion of crustal flow lifting the footwall of the seismogenic fault.
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