Subduction tractions and vertical axis rotations in the Zagros–Makran transition zone, SE Iran: the 2013 May 11 Mw 6.1 Minab earthquake

The source parameters and slip distribution of the 2013 May 11 Mw 6.1 Minab earthquake are studied using seismology, geodesy and field observations. We observe left-lateral strike-slip motion on a fault striking ENE–WSW; approximately perpendicular to previously studied faults in the Minab–Zendan–Palami fault zone. The fault that ruptured in 2013 is one of a series of ∼E–W striking left-lateral faults visible in the geology and geomorphology. These accommodate a velocity field equivalent to right-lateral shear on ∼N–S striking planes by clockwise rotations about vertical axes. The presence of these faults can reconcile differences in estimates of fault slip rates in the western Makran from GPS and Quaternary dating. The longitudinal range of shear in the western Makran is likely to be controlled by the distance over which the underthrusting Arabian lithosphere deepens in the transition from continent–continent collision in the Zagros to oceanic subduction in the Makran

Controls on the geometry and evolution of thin-skinned fold-thrust belts, and applications to the Makran accretionary prism and Indo-Burman Ranges

The formation of fold-thrust belts at convergent margins is a dynamic process. Accretion of weak sediments to the front of the overriding plate results in crustal thickening and continued flexural subsidence of the underthrusting plate. Fold-thrust belts are often treated as a Coulomb wedge having self-similar geometries with a critical taper, and either a rigid or isostatically compensated base. In this paper we build upon this work by developing a new dynamic model to investigate both the role of the thickness and material properties of the incoming sediment, and the flexure in the underthrusting plate in controlling the behaviour and evolution of fold-thrust belts. Our analysis shows that the evolution of fold-thrust belts can be dominated by either gravitational spreading or vertical thickening, depending on the relative importance of sediment flux, material properties and flexure. We apply our model to the Makran accretionary prism and the Indo-Burman Ranges, and show that for the Makran flexure must be considered in order to explain the dip of the sediment-basement interface from seismic reflection profiles. In the Indo-Burman Ranges, we show that incoming sediment thickness has a first-order control on the variations in the characteristics of the topography from north to south of the Shillong Plateau

Lateral variations in lower crustal strength control the temporal evolution of mountain ranges: examples from south‐east Tibet

Plain Language Summary - Abstract below The rocks which make up the Earth's continents move and change shape in response to tectonic forces. How rocks respond to these forces depends on their material properties, which can vary in space and time. These material properties, therefore, control the shape of mountain ranges, and how mountains grow. This study investigates why some mountain ranges have steep fronts, whilst others have gentle gradients. We look at how regions made up of strong rocks (such as the Sichuan Basin) affect the shape and growth of adjacent mountain ranges. We find that mountain ranges with steep fronts can form when weaker rocks move over stronger ones. Recent measurements of oxygen in ancient soils suggests that parts of the south‐eastern margin of the Tibetan Plateau (between the Sichuan Basin and the Central Lowlands of Myanmar) have been high since about 50 million years ago, and that the area has risen more slowly than has previously been estimated. In south‐east Tibet, the pattern of earthquakes, and how fast the mountains have grown, can be explained by these strong areas, without invoking complicated material properties in the mountain ranges. Such strong regions may be important in controlling the shape of mountain ranges globally. Abstract Controversy surrounds the rheology of the continental lithosphere, and how this rheology controls the evolution and behaviour of mountain ranges. In this study, we investigate the effect of lateral contrasts in the strength of the lower crust, such as those between cratonic continental interiors and weaker rocks in the adjacent deforming regions, on the evolution of topography. We combine numerical modelling with recently published results from stable‐isotope palaeoaltimetry in south‐east Tibet. Stable‐isotope palaeoaltimetry in this region provides constraints on vertical motions, which are required to distinguish between competing models for lithosphere rheology and deformation. We use numerical modelling to investigate the effect of lateral strength contrasts on the shape and temporal evolution of mountain ranges. In combination with palaeoaltimetry results, our modelling suggests that lateral strength contrasts provide a first‐order control on the evolution of topography in south‐east Tibet. We find that the evolution of topography in the presence of such strength contrasts leads to laterally‐varying topographic gradients, and to key features of the GPS‐ and earthquake‐derived strain‐rate field, without the need for a low‐viscosity, lower‐crustal channel. We also find that palaeoaltimetric samples may have been transported laterally for hundreds of kilometres, an effect which should be accounted for in their interpretation. Our results are likely to be applicable to the evolution of mountain ranges in general, and provide an explanation for the spatial correlation between cratonic lowland regions and steep mountain range‐fronts

Unexpected earthquake hazard revealed by Holocene rupture on the Kenchreai Fault (central Greece): Implications for weak sub-fault shear zones

High-resolution elevation models, palaeoseismic trenching, and Quaternary dating demonstrate that the Kenchreai Fault in the eastern Gulf of Corinth (Greece) has ruptured in the Holocene. Along with the adjacent Pisia and Heraion Faults (which ruptured in 1981), our results indicate the presence of closely-spaced and parallel normal faults that are simultaneously active, but at different rates. Such a configuration allows us to address one of the major questions in understanding the earthquake cycle, specifically what controls the distribution of interseismic strain accumulation? Our results imply that the interseismic loading and subsequent earthquakes on these faults are governed by weak shear zones in the underlying ductile crust. In addition, the identification of significant earthquake slip on a fault that does not dominate the late Quaternary geomorphology or vertical coastal motions in the region provides an important lesson in earthquake hazard assessment

Introducing Stories Into Downward Counterfactual Analysis: Examples From a Potential Mediterranean Disaster

How to recognise potential disasters is a question at the centre of risk analysis. Over-reliance on an incomplete, often epistemologically-biased, historical record, and a focus on quantified and quantifiable risks, have contributed to unanticipated disasters dominating both casualties and financial losses in the first part of the 21st century. Here we present the findings of an online workshop implementing a new scenario-planning method, called downward counterfactual analysis, which is designed to expand the range of risks considered. Interdisciplinary groups of disaster researchers constructed downward counterfactuals for a present-day version of the 365CE Cretan earthquake and tsunami, imagining how these events might have been worse. The resulting counterfactuals have trans-national, long-term impacts, particularly in terms of economic losses, and connect risks previously identified in separate sectors. Most counterfactuals involved socio-political factors, rather than intrinsic components of the hazard, consistent with the idea that there are “no natural disasters”. The prevalence of cascading counterfactuals in our workshop suggests that further work is required to give the appropriate weight to pre-existing economic and social conditions in scenario-planning methods, such as downward counterfactual analysis, which focus on the occurrence of a hazard as the temporal starting point for a disaster. Both proposed counterfactuals and their justifications reflect a bias towards contemporary issues and recent historical disasters. We suggest that interdisciplinary groups can expand the range of imagined risks. However, the setup used here would be improved by including local stakeholders. Qualitative forms of downward counterfactual analysis have potential applications for community engagement and education, as well as for risk analysis.</jats:p

Combining remote sensing techniques and field surveys for post‑earthquake reconnaissance missions

Remote reconnaissance missions are promising solutions for the assessment of earthquake induced structural damage and cascading geological hazards. Space-borne remote sensing can complement in-field missions when safety and accessibility concerns limit post-earthquake operations on the ground. However, the implementation of remote sensing techniques in post-disaster missions is limited by the lack of methods that combine different techniques and integrate them with field survey data. This paper presents a new approach for rapid post-earthquake building damage assessment and landslide mapping, based on Synthetic Aperture Radar (SAR) data. The proposed texture-based building damage classification approach exploits very high resolution post-earthquake SAR data integrated with building survey data. For landslide mapping, a backscatter intensity-based landslide detection approach, which also includes the separation between landslides and flooded areas, is combined with optical-based manual inventories. The approach was implemented during the joint Structural Extreme Event Reconnaissance, GeoHazards International and Earthquake Engineering Field Investigation Team mission that followed the 2021 Haiti Earthquake and Tropical Cyclone Grace

Combining remote sensing techniques and field surveys for post-earthquake reconnaissance missions

Remote reconnaissance missions are promising solutions for the assessment of earthquake-induced structural damage and cascading geological hazards. Space-borne remote sensing can complement in-field missions when safety and accessibility concerns limit post-earthquake operations on the ground. However, the implementation of remote sensing techniques in post-disaster missions is limited by the lack of methods that combine different techniques and integrate them with field survey data. This paper presents a new approach for rapid post-earthquake building damage assessment and landslide mapping, based on Synthetic Aperture Radar (SAR) data. The proposed texture-based building damage classification approach exploits very high resolution post-earthquake SAR data integrated with building survey data. For landslide mapping, a backscatter intensity-based landslide detection approach, which also includes the separation between landslides and flooded areas, is combined with optical-based manual inventories. The approach was implemented during the joint Structural Extreme Event Reconnaissance, GeoHazards International and Earthquake Engineering Field Investigation Team mission that followed the 2021 Haiti Earthquake and Tropical Cyclone Grace

Red-flag sepsis and SOFA identifies different patient population at risk of sepsis-related deaths on the general ward

Controversy exists regarding the best diagnostic and screening tool for sepsis outside the intensive care unit (ICU). Sequential organ failure assessment (SOFA) score has been shown to be superior to systemic inflammatory response syndrome (SIRS) criteria, however, the performance of “Red Flag sepsis criteria” has not been tested formally. The aim of the study was to investigate the ability of Red Flag sepsis criteria to identify the patients at high risk of sepsis-related death in comparison to SOFA based sepsis criteria. We also investigated the comparison of Red Flag sepsis to quick SOFA (qSOFA), SIRS, and national early warning score (NEWS) scores and factors influencing patient mortality. Patients were recruited into a 24-hour point-prevalence study on the general wards and emergency departments across all Welsh acute hospitals. Inclusion criteria were: clinical suspicion of infection and NEWS 3 or above in-line with established escalation criteria in Wales. Data on Red Flag sepsis and SOFA criteria was collected together with qSOFA and SIRS scores and 90-day mortality. 459 patients were recruited over a 24-hour period. 246 were positive for Red Flag sepsis, mortality 33.7% (83/246); 241 for SOFA based sepsis criteria, mortality 39.4% (95/241); 54 for qSOFA, mortality 57.4% (31/54), and 268 for SIRS, mortality 33.6% (90/268). 55 patients were not picked up by any criteria. We found that older age was associated with death with OR (95% CI) of 1.03 (1.02–1.04); higher frailty score 1.24 (1.11–1.40); DNA-CPR order 1.74 (1.14–2.65); ceiling of care 1.55 (1.02–2.33); and SOFA score of 2 and above 1.69 (1.16–2.47). The different clinical tools captured different subsets of the at-risk population, with similar sensitivity. SOFA score 2 or above was independently associated with increased risk of death at 90 days. The sequalae of infection-related organ dysfunction cannot be reliably captured based on routine clinical and physiological parameters alone