Fault Movement Research Articles

Imaging the Fault Zone Structure of the Pearl River Estuary Fault in Guangzhou, China, from Waveform Inversion with an Active Source and Dense Linear Array

Since high-resolution structure imaging of active faults within urban areas is vital for earthquake hazard mitigation, we perform a seismic survey line crossing the Pearl River Estuary Fault (PREF) in Guangzhou, China. First, ten shots of a new and environmentally friendly gas explosion source are excited with about 1 km spacing and recorded by 241 nodal short-period seismometers with an average spacing of 60 m. Then, based on these acquisition data, we adopt waveform inversion to explore the kinematic and dynamic information of early arrival wavefields to recover the subsurface structures. The inversion results indicate that while the low-velocity zone (LVZ) in depth surrounding the PREF is 2.5 km in width and extended to 0.7 km, another LVZ of 1.5 km in width and extended to 0.7 km in depth is surrounded by the Beiting–Nancun fault. We observe that the analysis of evolution and activities of the fault systems reveal no historical earthquakes in our study area; we interpret that the two LVZs controlled by the faults are probably attributed to the fluid dynamics, sediment source, and fault motion at different geological times, rather than fault-related damage zones. The results can provide significant basis for earthquake prevention and hazard assessment in Guangzhou. The finding also shows that the waveform inversion can effectively explore the fine structure of active faults in urban area with dense linear array and spare active source excitations.

ПРОДОЛЬНЫЕ СДВИГИ В ОСТРОВНОЙ ДУГЕ ПРИ НОРМАЛЬНОМ ПОДДВИГЕ ОКЕАНИЧЕСКОЙ ПЛИТЫ: ПРИМЕР КАМЧАТКИ

Crustal deformation in Kamchatka since the Middle Pleistocene is driven by two processes: transverse extension as a result of its eastern part displacement towards the ocean following the submerged part of the oceanic plate, and transverse shortening just north of the subduction zone as the Komandor block of the Aleutian arc gets closer to Kamchatka. The areas of differently directed movements and deformations of Kamchatka are separated by the left-lateral horizontal flexure appearing in plan as curved uplifts of the Eastern Range, the deep water trench, and consequently, the axis of the East volcanic belt. Kinematically, the flexure replaces the expected transverse left-lateral strike-slip fault between the two differently deformed parts of Kamchatka. The revealed right-lateral displacements along the longitudinal faults in the northern part of the uplift of the Eastern Range in Kamchatka result from bedding-plane slip in the flexure limb. The high alluvial terrace of the Kamchatka River, displaced landforms, and faulted layers of the soil-pyroclastic cover were dated by the tephrochronological method. Age determinations imply that the recurrence of displacements along the faults of the flexure is about once every 3-5 thousand years, and the average rate of lateral displacements during the second half of the Holocene is about 1 mm per year. Comparison of the fault movement rates and the maximum value of the accumulated lateral displacement of the Kamchatka River valley suggest that horizontal movements began no later than the second half of the Middle Pleistocene. This also means that the Kamchatka River valley already existed at that time, and its antecedent part was formed when down-cutting into the bedrock of the uplifting Eastern Range. The total amount of displacement along the faults of the flexure since the second half of the Middle Pleistocene is estimated at about 1 km. On the whole, the results suggest the possibility of lateral movements along longitudinal faults in an island arc with the oceanic plate direction being normal to it.

LATE QUATERNARY ACTIVITY OF THE HARAMACHI SEGMENT OF THE FUTABA FAULT IN NORTHEAST JAPAN THROUGH TOPOGRAPHIC ANAGLYPH IMAGES AND BOREHOLE CORE SEDIMENT ANALYSIS

The Haramachi Fault segment in the northeastern part of Honshu Island, Japan, has mainly sinistral fault movements with minor reverse component within the Futaba Fault Zone in the northeastern Japan arc. The 2011 Mw 9.0 earthquake occurred off the Pacific coast of Tohoku which caused large crustal deformations. Despite being the closest active fault to the epicenter, very limited investigation has been conducted on the Futaba Fault Zone. Previous studies used smaller scale topographic maps and fault activity was estimated only from trenching and borehole investigations in the central part of the Haramachi Fault segment. Thus, geometry, kinematic, and recent tectonic activity of the fault segment is not well identified, especially in northern part. In this study, we use a combination of high-resolution DEMs (2-m and 5-m mesh), several types of topographic anaglyph images (slope, negative and positive openness), and conducted field survey to confirm remote sensing interpretation. Subtle surface expression of deformation associated with active faulting, such as deformed terrace risers, deflected drainages, and small fault scarps can now be identified more clearly. Several new fault strands in the northern part of the segment were found supported by fault outcrops found in the field confirming the recent activity of the fault system. The new estimation of the total length of the Haramachi segment produced from the approach of this study yields 25 km, which is capable of producing Mw 6.5 – 7.0 or Mjma 7.2 earthquakes if ruptures were to occur altogether in the future. Moreover, a shallow borehole survey and radiocarbon dating from the soil organic material has revealed the minimal timing estimation of the most recent faulting in the Haramachi segment to be 3694 ± 24 BP. This research provides a revised understanding of active fault distribution and deformation associated with the Haramachi segment and validates the timing of the most recent faulting event more broadly.

Design of offshore gas pipelines against active tectonic fault movement

Active tectonic faults impose permanent ground actions on offshore gas pipelines that threaten their safety and service life. The seismic fault movement deforms the pipeline and causes excess strains due to bending, along with axial compressive or tensile forces depending on the fault type. This may lead to buckling, severe cross-sectional distortion and even rupture. The assessment of an offshore pipeline crossing active faults considers the estimation of the potential fault displacement, the structural response of the pipeline, and the limit-state capacity. This paper explores the design options for improving the capacity of partially embedded offshore pipelines to tolerate fault differential displacement using equations that are fitted to the results of finite element simulations and allow the prediction of the critical co-seismic fault displacement, i.e. the value of fault displacement that leads to various forms of pipeline failure. Considering all the types of faults, the influence of the parameters affecting the performance of an offshore pipeline subjected to active seismic fault rupture is quantified and discussed. The proposed equations could be used as guidance in the preliminary route design of future medium-diameter offshore pipelines and in the assessment of the vulnerability of existing ones. An illustrative example is also presented to demonstrate the application of the proposed equations.

Detachment levels of Colombian caribbean mud volcanoes

Regional analysis of mud volcanoes demonstrates the regional extension of these processes in Northern Colombia. Mud volcanoes are active systems that manifest the characteristics of the underlying sedimentary sequences on the surface, as well as the presence of hydrocarbons. These may which provide information about the oil systems and the characterization of new migration paths. New data acquired during field geology studies, along with the evaluation of acquired aerial images by dron, allowed to observe variations in terms of morphology and neotectonic process, being distinctive between mud volcanoes formed in different structural domains. Mud volcanoes formed in areas of basement without thrust faults (back stop zone) are usually circular, connected to the basement by regional faults. Other mud volcanoes formed in older and younger deformed belts tend to present ellipsoidal shapes, with drainages patterns that suggest local stress fields associated with regional strike slip movements of major faults. The analysis of U/Pb ages in detrital zircons extracted from mud volcanoes and outcropping sedimentary sequences in the Colombian Caribbean, together with the analysis of foraminiferal and palynomorph faunas, suggest different levels of detachment. Clay mineralogy and geochemistry indicate that mud volcanoes formed in the back stop and the Northern part of the San Jacinto deformed belt have sludge material originated in sedimentary sequences with contributions from continental basement rocks, while the mud volcanoes located in the central and Southern parts of the studied area tend to show sediments provided from deepest stratigraphic levels, derived from less evolved magmatic sources (dioritic basements). Gas and water analysis obtained from studied mud volcanoes suggest that the old deformed belt, Paleocene accretionary wedge and back stop areas, have evidences of thermogenic oil systems, while in the domain of the younger deformed belt the tendency is to indicate evidences of microbial process.

Automatic Fault Plane Solution for the Provision of Rapid Earthquake Information in South Korea

The Korea Meteorological Administration (KMA) provides detailed hypocenter information after the earthquake early warning (EEW) service, due to increased public interest and for the study of fault movements. However, the rapid production of hypocenter information has limitations, including the necessity for the calculation of focal mechanisms, which requires expertise in seismology. Therefore, we developed automatic focal mechanisms (AFMs) based on the time domain moment tensor inversion method. A key feature of AFMs is the automatic collection and reforming of waveform data using information for EEW. Furthermore, we propose an additional module of the iterative inversion by reducing the low variance reduction data. This shows the increased variance reduction value rather than that of the first inversion. The variance reductions for the first inversion results were between 59 and 94%, whilst the results of the second inversion using the additional module were increased to 79–97%. The accuracy of the automatic results was similar to that of the manually determined results and was well adapted to the local earthquakes in and around the Korean Peninsula. The KMA provided the focal mechanisms of local earthquakes that could then be automatically determined using the EEW information within approximately 6–8 min and subsequently reported.

Slow Fault Slip Signatures in Coseismic Ionospheric Disturbances

AbstractRise times of earthquake moment release influence the spectra of seismic waves. For example, slow fault movements in tsunami earthquakes excite larger tsunamis than expected from intensities of short‐period seismic waves. Here we compare amplitudes of two different atmospheric waves, long‐period internal gravity waves and short‐period acoustic waves, excited by coseismic vertical crustal movements. We observe them as coseismic ionospheric disturbances by measuring ionospheric electrons using global navigation satellite systems. Four regular megathrust earthquakes Mw 8.0–9.0 showed that the internal gravity waves become ten times stronger as the magnitude increases by one. We found that the 2010 Mentawai earthquake, a typical tsunami earthquake, excited internal gravity waves stronger than those expected by this empirical relationship. On the other hand, amplitudes of acoustic waves excited by tsunami earthquakes were normal. This suggests that slow fault ruptures excite long‐period atmospheric waves efficiently, leaving a slow earthquake signature in ionospheric disturbances.

Paleostress Analysis in the Northern Birjand, East of Iran: Insights from Inversion of Fault-Slip Data

This research assessed stress regimes and fields in eastern Iran using fault-slip data and the tectonic events associated with these changes. Our stress analysis of the brittle structures in the Shekarab Mountains revealed significant changes in stress regimes from the late Cretaceous to the Quaternary. Reconstructing stress fields using the age and sense of fault movements showed that during the late Cretaceous, the direction of the maximum horizontal stress axes (σ1) under a compressional stress regime was ~N290°. This stress regime led to the uplifting of ophiolites and peridotites in eastern Iran. During the Eocene, the σ1 direction was NE-SW. The late Eocene and Oligocene stress states showed two distinct transpression and transtension stress regimes. This transition from transpression to transtension in the eastern Shekarab Mountains was the consequence of regional variations in stress regimes. The Quaternary stress state indicates that the tectonic regime in the Quaternary is strike-slip and the σ1 direction is ~N046°, which coincides with the current convergence direction of the Arabia–Eurasia plates. Our paleostress analysis revealed that four distinct stress regimes have been recognized in the area, including compressional, transtensional, transpressional, and strike-slip regimes. Our findings indicated that the diversity of the tectonic regimes was responsible for the formation of a variety of geological structures, including folds with different axes, faults with different mechanisms, and the current configuration of the Sistan suture zone.

Interferometric Synthetic Aperture Radar (InSAR) applications for mapping of terrain displacement in mineral deposits

The Interferometric Synthetic Aperture Radar (InSAR) applications for mapping of terrain displacement have been tested on the Vlaykov Vruh and Tsar Assen porphyry-copper deposits to test terrain displacements and possible fault movements. Time series for each area have been prepared to display the evolution of displacement over time, for a given point for both Cu-porphyry outcrops.

Pit Crater Chains Across the Solar System: Evidence for Subterranean Tectonic Caves, Porosity and Permeability Pathways on Planetary Bodies

AbstractPit crater chains are surface features comprised of linear assemblages of collapsed depressions that are identified on several solid bodies throughout the Solar System. On Earth, they have been observed to form when dilational motion on normal faults causes the overlying materials to collapse into the dilating segment of the buried fault. It has been hypothesized that pit crater chains observed on Mars, Enceladus, and various small bodies formed by the same process. Dilational fault movement can also create subsurface permeability pathways for fluid/volatile transport and trapping. Studying pit crater chains and tectonic caves on planetary bodies has implications for both in situ resource utilization and astrobiology, and should be considered as a potential driver for determining exploration targets.

Intraplate Crustal Deformation In Sabah: Preliminary Results Of Global Positioning System/Global Navigation Satellite System Measurements In The Ranau Area

The Ranau area is one of the most earthquake-prone areas in Sabah due to the ongoing intraplate deformation in the region. Numerous active faults have been mapped here, but to date these faults are yet to be fully documented in terms of their exact locations and movements. Since 2018, the Department of Mineral and Geoscience (JMG) has installed and monitored 31 GPS/GNSS (Global Positioning System/Global Navigation Satellite System) monuments in the Ranau area to determine crustal movements in this region. Preliminary results show minor horizontal and vertical movements (ranging from 0.1 cm to 4.3 cm) indicating that the Ranau area is undergoing intraplate crustal deformation due to both NW-SE compressional and extensional tectonics. A clear demarcation of upward and downward vertical movements recorded in areas to the NW and SE of Kundasang could be related to uplift and subsidence associated with a large open anticline and syncline. A consistent northwestward horizontal movement from Kundasang to Kota Belud indicates the presence of a single crustal block moving away from the NE-SW trending Lobou-Lobou Fault Zone. Southwestward horizontal movement in the Nalapak-Nabutan area indicates the presence of a NW-SE trending fault possibly associated with the Matupang Fault Zone. These preliminary results show that the GPS/GNSS campaign has proven to be quite successful in locating the major earthquake-generating faults in the Ranau area. However, the locations and nature of the movements of other active faults are still uncertain. It is hoped that the activity of these faults will become clearer after a few more years of monitoring.

GEOMORPHOLOGY AND CHARACTERISTICS OF NICKEL LATERITE IN BAINGKETE VILLAGE, MAKBON DISTRICT, SORONG REGENCY WEST PAPUA PROVINCE

Nickel deposits geologically came from weathering of abducted ultrabasic igneous rock. The rock is exposed during removal, followed by a geomorphological process that develops laterazation. Geologically the Makbon area is on the path of the Sorong horizontal fault field which has been active since the beginning of the Miocene. The dominant Sorong fault movement to the west exposed ocean floor rocks including blocks of ultrabasic rock. To determine the mineralization of nickel laterite in the Makbon area, this study combines mapping and surface geological observation methods with XRF analysis in the laboratory. The results of the study are known that the research area is composed of six land formations, namely the Makbon Fault Block Ridge, Baingkete Fault Block Ridge, Bancuh Baingkete Hills, Baingkete Bald Mountain Bancuh Hills, Makbon Fault Structure Denudation Plain, and Dore Bay Hills. Geomorphological control of the distribution of laterite nickel on steep slopes produces a thin, thickened laterite layer on the topography of the ramps. The characteristics of laterite nickel deposits in Baingkete Village are Type A deposits (Mg-Ni Silicate), on serpentinite bedrock, which consist of laterite profiles of limonite zone, saprolite zone, and bedrock zone

Determination of effect of the movement of an infinite fault in viscoelastic half space of standard linear solid using fractional calculus

The subsurface deformation which is observed in seismic region during aseismic period has a great impact on displacement and stress-strain accumulation due to earthquake fault movement. In this paper we have considered a theoretical model of aseismically creeping, buried, inclined, infinite strike-slip fault located in viscoelastic half space of standard linear-solid medium. Our main objective is to find the analytical solutions of displacement, stresses, strains (a) in the absence of any fault movement and (b) after the commencement of fault movement with the help of Laplace transformation and Green’s function technique using fractional calculus taking Mittag-Leffler function and then to determine numerical results of displacement, stresses and strains with different creep velocities for various inclinations of the fault using suitable model parametric values ([3, 7, 12, 26]). It is observed that the fault in our model exceeds the critical stress at about 117 years if it is a vertical fault while at about 141 years if the fault is inclined at an angle with the free surface. A comparative study has been done and the numerical results are found to be in good agreement . This study may help in developing the earthquake prediction program.

Characteristics of stress field and crustal kinematics of the southern region of Sichuan-Yunnan block, southern Tibet Plateau

The Red River fault is a massive tectonic shear zone of the Sichuan-Yunnan block, southern Tibet Plateau. The target area of this study is the Red River fault's middle-northern section and adjacent areas. Considering the spatial difference of tectonic structures and the inhomogeneity of focal mechanism solutions, we divided the target area into three structural units: the northern extension area, the middle strike-slip movement area, and the west complex rupture area. The study is carried out on the basis of zoning. Using the CAP method to invert the focal mechanism of moderate earthquakes and the principal compressive and tensile stress. Restoring the seismic source spectrum of small and medium earthquakes, then inversion the stress drops in three sub-units based on Brune model using digital waveform records. Our study suggests that: (1) Many high-stress drop earthquakes occurred in the transitional areas from the Weixi-Qiaohou fault to the Red River fault and from the Chuxiong fault to the Qujiang fault, also occurred in the Changning-Baoshan-Yongping area, revealing a large accumulation of local tectonic stress. (2) Some events with Δσ ≥ 20 MPa have occurred in the prominent low-speed anomaly area, indicating that a passive deformation crossed the Red River fault and extended to the west. Yangbi MS 6.4 earthquake (2021) occurred in a strongly locked area with high potential earthquake risk. (3) In the north of the study region, the movement of the Sichuan-Yunnan block to SE-SSE orientation was governed by the dextral strike-slip movement of the NW strike fault; in the middle region, the SE-orientated movement of the block relative to the South China block was governed by the sinistral slip movement of the SN-strike faults; and in the west region, the tectonic stress was governed by clockwise rotation of the block and the sinistral slip movement of the NE strike faults. We suggest that strike slip and rotation of the Red River fault's middle section may drive and aggravate passive movement in the north section, resulting in locally geophysical field responses. Therefore, the potential risk of a large earthquake in the middle-northern section of the Red River fault should be monitored.

SLIP SURFACE IDENTIFICATION FOR LANDSLIDE HAZARD MITIGATION WITH ELECTRICAL RESISTIVITY TOMOGRAPHY

Pidada area, Panjang sub-district, Bandar Lampung city, located on Barisan Hill complex, has been affected by the Sumatran fault movement and the Lampung-Panjang fault so that the morphological condition is hilly with steep slopes, which causes the risk of natural disasters such as landslides. In this article, the identification of subsurface rock lithology and sliding plane in the landslide-prone zone is carried out using the Wenner-Schlumberger configuration geoelectric method. Based on the Wenner-Schlumberger configuration, the top layer has lithology clay tuff and sandy tuff, which predicted a weathered rock with a resistivity of 1 - 133 ohm.m. Coarse-grained tuff and fine-grained tuff with resistivity values of 135 - 250 ohm.m in the middle. The bottom layer has a resistivity of more than 250 ohm.m, that predicted to have a lithology breccia (igneous rock) Tarahan Formation. The sandy clay layer (81 - 90 ohm.m) predict as a sliding plane in this area at depths of 8.2 to 16 m. The type of landslide developed in the research area is a crawling soil landslide with very steep slope characteristics (80 – 350).

The 2022 Twin Earthquakes and Tectonic Environment in Kyaing Tong Basin, Eastern Myanmar

The first earthquake of magnitude 4.8 struck at 57 km south of Kyaing Tong, latitude 21.1141°N longitude 99.850°E, on 21st July 2022, at 16:40:08 UTC ( 11:07 a.m. local time ) at the depth of 10 km. Immediately after 30 minutes on the same day of 21st July 2022, the second earthquake with magnitude 5.9 occurred, 53 km south of Kyaing Tong at latitude 21.150°N 99.863°E, 17:07:26 UTC (11:37 a.m. local time) at 10 km depth. Focal mechanism solution for the first event was left-lateral strike-slip faulting and the second by normal faulting with a component of strike-slip component (United States Geological Survey). Many lesser aftershocks followed the main shocks and continued since July and still ongoing up to date in 2022. Twin earthquakes ruptured along the Wan Ha fault which bounds the southeast side of the Kyaing Tong basin, eastern Myanmar. The rupture propagated southward. The Kyaing Tong basin is one of the tectonic basins in the Paleo-Tethys suture zone in eastern Myanmar. These earthquakes are due to the movement of Wan Ha fault, affected the town Kyaing Tong where it caused some houses and schools collapsed. No casualty was reported. According to data from USGS, and other earthquake agencies, there is a clear increase in detected earthquakes, particularly smaller quakes of magnitude around ≥ 1.0 and ≥ 2.0 at shallower depth of 1000 meter. From the studies of satellite images, aerial photographs, shaded relief map and Digital Elevation Model map, several lineaments are visible and detailed mapping of these lineaments show the strike-slip faults in ENE-WSW direction and normal faults in NE-to NNE-striking direction. NW-SE extension is evident by the occurrence of brittle normal faults and NE-to ENE-oriented sinistral strike-slip fault. Within this zone is the trace of regional compression in a NE-SW direction. This region is presently undergoing active tectonic deformation, as indicated by current seismicity and earthquake focal mechanism solution.

Slip Rate of Kumering Fault in Lampung Province Calculated from GPS Data from 2007 to 2021

Kumering Fault in Lampung Province is a segment of SFZ that was tectonically active region that had generates large earthquakes. The earthquake hazard around Kumering Fault can be estimated by understanding slip rate of Kumering Fault. This research aim is to estimate slip rate of Kumering Fault by using GPS data from 2007 to 2021. GPS data used in this research are 6 periodic GPS sites and 1 continuous Sumatran GPS Array site. GPS data is processed to obtain daily solution coordinates which are used to calculate velocity by using least-square method of linear regression. Fault parallel velocities are calculated to estimate slip rate and locking depth of Kumering Fault. The The process to obtain slip rate is using grid-search method by finding best fit velocities for all GPS sites. The velocities of GPS sites indicate Sundaland Plate movement. Fault parallel velocities shows the typical movement of right-lateral Kumering Fault. The slip rate of Kumering Fault estimated from this study is 18.2 ± 10 mm/year while the locking depth of the Kumering Fault is 17 ± 3 km. It proves that SFZ is rigid block. However, building more GPS sites in area study is mandatory to obtain better result.

Real-Time Source Modeling of the 2022 Mw 6.6 Menyuan, China Earthquake with High-Rate GNSS Observations

On 7 January 2022, a Mw 6.6 earthquake struck Menyuan County in the Qinghai province of China and the earthquake caused severe damage to infrastructures. In this study, the performance of the high-rate global navigation satellite system (GNSS) on real-time source modeling of the 2022 Mw 6.6 Menyuan earthquake was validated. We conducted the warning magnitude calculation, centroid moment tensor (CMT) inversion, and static fault slip distribution inversion using displacements collected from 14 1-Hz GNSS stations. Our results indicate that the warning magnitude derived from the peak ground displacement (PGD) first exceeds Mw 6.0 approximately 9 s after the earthquake and tends to be stable after about 45 s. The derived finally stable magnitude is Mw 6.5, which is near the USGS magnitude of Mw 6.6. Based on the inverted CMT and static fault slip distribution results, it can be determined that the 2022 Menyuan earthquake is a left-lateral strike-slip event after about 20 s of the earthquake. Although the fault slips, inverted with the 30-s smoothed coseismic offsets, are unstable after about 40 s, all the inverted slip models after that time present the obvious surface rupture and the most fault motions are concentrated between the depth of 0 km and 8 km. Compared with the results inverted with the 30-s smoothed coseismic offsets, the CMT and fault slips inverted with the 70-s smoothed coseismic offsets are more stable. The results obtained in this study indicate that the high-rate GNSS has the potential to be used for real-time source modeling for earthquakes with a magnitude less than 7; the stability of the inverted CMT and fault slips can be improved by using the coseismic offsets averaged by a relatively long-time sliding window.

Topographic evidence of long wavelength active folding in the New Madrid seismic zone, intraplate North America

The northeast-striking Axial and Bootheel faults (AF and BHF) in the central USA are components of the New Madrid seismic zone (NMSZ) fault complex, source of M > 7 earthquakes in 1811–1812. Previous work shows Holocene displacement of the AF and BHF to be primarily right-lateral strike-slip movement west and south of the NMSZ restraining bend. In this study, treads of two Late Pleistocene alluvial terraces of the Mississippi River, the 14–16 ka Kennett and the 12 ka Morehouse terraces, were used as structural datums to assess any long-wavelength vertical component of deformation across these two faults. Using 10 m-resolution LiDAR, we constructed a best-fit polynomial trend surface of these terrace treads. Our results reveal a subtle ≤4 m-deep, 40 km-wide, 190 km-long, topographic trough. In the south, it corresponds to the southern segment of the AF and parallels the BHF for 50 km. Farther north it corresponds to a syncline in subsurface Paleozoic strata 10 to 20 km northwest of and parallel to the BHF.The trough axis crosses obliquely down-valley from the younger Morehouse terrace to the older Kennett terrace and does not correspond to major drainages. Significantly, the Malden-Bernie fluvial scarp separating the two terraces continues into the trough but is down-warped, inconsistent with an erosional origin of the trough. Along the southern segment of the trough, the older Kennett tread is topographically lower than the Morehouse tread, but relict Kennett braided channels were not buried during deposition of younger Morehouse alluvium. This suggests the Kennett terrace tectonically subsided along the trough after Morehouse terrace deposition. We interpret this trough as a subtle syncline along the western margin of the NMSZ restraining bend that developed in response to down-on-the-northwest fault movement after deposition of Morehouse alluvium.

Shaking and splashing—A case study of far‐field effects of the Mjølnir asteroid impact on depositional environments in the Barents Sea

AbstractThe Mjølnir impact crater in the Norwegian Barents Sea features among the 20 largest impact craters listed in the Earth Impact Database. The impact is dated to 142 ± 2.6 Ma, corresponding closely to the Jurassic/Cretaceous boundary in the Boreal stratigraphy. Multidisciplinary studies carried out over the last three decades have suggested that the up to 40 km wide crater was created by a 1–3 km diameter impactor colliding with a shallow epicontinental sea, causing regional havoc and a regional ecological crisis that followed in its wake. Only minor evidence for the consequences of the impact for the surrounding depositional basins has been documented so far. This study describes a large submarine slump penetrated by hydrocarbon exploration well 7121/9‐1, located in the southern Hammerfest Basin and approximately 350 km away from the impact site. The slump is dated by a black shale drape, which contains characteristic impact‐related biotic assemblages and potential ejecta material. This precise dating enables us to associate the slump with large‐scale fault movements and footwall collapse along the basin‐bounding Troms‐Finnmark Fault Complex, which we conclude were caused by shock waves from the Mjølnir impact and the passage of associated tsunami trains. The draping black shale is interpreted to represent significant reworking of material from the contemporary seabed by tsunamis and currents set up by the impact.