Magnetotelluric impedance tensor analysis for identification of transverse tectonic feature in the Wagad uplift,Kachchh, northwest India

The 2001 Bhuj earthquake (Mw 7.7) occurred in northwestern region of Indian peninsula has reactivated a couple of transverse faults to its surroundings. Intermediate to moderate magnitude earthquakes are occurring along these faults which includes recent Dholavira earthquake (Mw 5.1, 2012) suggesting distinct tectonic scenario in the region. We present the results of magnetotelluric (MT) impedance tensors analyses of 18 sites located along a profile cutting various faults in the uplifted Wagad block of the Kachchh basin. The MT time series of 4–5 days recording duration have been processed and the earth response functions are estimated in broad frequency range (0.01–1000 s). The observed impedance tensors are analyzed by using three decomposition techniques as well as by the phase tensor method constraining with the induction arrows. The analyses suggest distinct tectonic feature within the block bounded by the South Wagad Fault (SWF) and the North Wagad Fault (NWF) particularly in the period band of 1–10 s. In the south of NWF, the telluric vectors and the major axes of the phase ellipses are aligned in the NNW–SSE to NW–SE direction where as a dominant E–W strike is obtained for northern side of the NWF. The transverse geo-electric strike coincides with the prominent clustering of seismicity after the Bhuj earthquake and trend of the Manfara transverse fault is located in close vicinity of the study area. We therefore suggest the presence NNW–SSE trending transverse structural feature in the Wagad uplift of the basin appears to play significant role in the current seismicity of the active intraplate region.     

Seismic profile analysis of the Kangra and Dehradun re-entrant of NW Himalayan Foreland thrust belt,India: A new approach to delineate subsurface geometry

In the NW Sub-Himalayan frontal thrust belt in India, seismic interpretation of subsurface geometry of the Kangra and Dehradun re-entrant mismatch with the previously proposed models. These procedures lack direct quantitative measurement on the seismic profile required for subsurface structural architecture. Here we use a predictive angular function for establishing quantitative geometric relationships between fault and fold shapes with ‘Distance–displacement method’ (D–d method). It is a prognostic straightforward mechanism to probe the possible structural network from a seismic profile. Two seismic profiles Kangra-2 and Kangra-4 of Kangra re-entrant, Himachal Pradesh (India), are investigated for the fault-related folds associated with the Balh and Paror anticlines. For Paror anticline, the final cut-off angle \(\beta =35{^{\circ }}\) was obtained by transforming the seismic time profile into depth profile to corroborate the interpreted structures. Also, the estimated shortening along the Jawalamukhi Thrust and Jhor Fault, lying between the Himalayan Frontal Thrust (HFT) and the Main Boundary Thrust (MBT) in the frontal fold-thrust belt, were found to be 6.06 and 0.25 km, respectively. Lastly, the geometric method of fold-fault relationship has been exercised to document the existence of a fault-bend fold above the Himalayan Frontal Thrust (HFT). Measurement of shortening along the fault plane is employed as an ancillary tool to prove the multi-bending geometry of the blind thrust of the Dehradun re-entrant.     

Iterative selective spatial variance reduction of MYD11A2 LST data

The aim of this research effort is to develop a method that will allow to map and evaluate thermal anomalies in SW USA from the MYD11A2 night land surface temperature (LST) imagery being available for the year 2014, that present higher spatial (1 km) and temporal (46 images per year) resolution than the MYD11C3 LST data (12 images per year at 5.6 km spatial resolution). The fact that is MYD11A2 LST imagery is projected to a rectangular grid did not affect the X, Y and elevation (H) spatial decorrelation stretch. Principal component analysis and linear regression models isolated and removed the X, Y, H (spatial) dependent variance included in the data while metrics devised verified the selective spatial variance reduction. The reconstructed 46 LST images represent the amount the LST deviates from the X, Y and H predicted for the year 2014. The thematic information content of the reconstructed LST images is verified by cluster analysis and mapped the spatial extend and the temporal variability of thermal anomalies within the study area. The positive thermal anomaly clusters are spatially arranged mainly west of Sierra Nevada in Great Basin Section where extensional tectonics create a series of titled elongated mountain blocks along the N to S direction in between basins bounded by normal faults, while the negative thermal anomaly clusters are spatially arranged along the coastal region, further north and in the western region far from the tilted mountain tectonic blocks of the Great Basin Section. The spatial maps that define regions with (positive or negative) thermal anomalies and distinct mean land response could assist landcover studies and support urban and rural planning in the context of emerging climatic change.     

Detecting the water depth of the South China Sea reef area from WorldView-2 satellite imagery

The accurate and efficient detection of the water depth of coral reefs through remote sensing imagery is crucial for navigation, marine engineering, and marine safety, among others. This study proposed a water depth inversion method that is processed using a two-step strategy. First, a log-dual-band ratio transform model is employed by combining blue, yellow, red, and red edge bands. Second, a multivariable linear regression model is constructed to determine water depth. The experimental study is conducted in a reef island in the South China Sea, and the WorldView-2 satellite data is used as the test data. Results demonstrated that the proposed method needs a few parameters in the model, and can effectively and reliably characterize the correlation between the spectral features and water depth.     

A Comparative Study of Landsat‐7 and Landsat‐8 Data Using Image Processing Methods for Hydrothermal Alteration Mapping

Comparing spaceborne satellite images of Landsat‐8 Operational Land Imager (OLI) and Landsat‐7 Enhanced Thematic Mapper plus (ETM+) was undertaken to investigate the relative accuracy of mapping hydrothermal alteration minerals. The study investigated the northern part of Rabor, which contains copper mineralization occurrences, and is located in the Kerman Cenozoic magmatic assemblage (KCMA), Iran. Image processing methods of band ratio, principal component analysis (PCA), and spectral angle mapper (SAM) were used to map the distribution of hydrothermally altered rocks associated with the porphyry copper mineralization. The band ratio combination of both sensors for mapping altered areas showed similar outcomes. PCA exposed variations in the spatial distribution of hydroxyl‐bearing minerals. The representation of hydrothermal areas using OLI data was more satisfactory than when using ETM+ data. SAM analysis found similar results for mapping hydroxyl‐bearing zones. Verification of the results came through ground investigation and laboratory studies. Rock samples (n = 56) were collected to validate results using thin sections, X‐ray diffraction (XRD) and spectral analyses. Field observations and laboratory analysis revealed that phyllic and propylitic alterations dominate the alteration zones in the study area. Argillic and iron oxides/hydroxides alterations were observed to a lesser degree. The results indicate that alteration maps prepared by OLI data using PCA for visual interpretation are more suitable than those of ETM+ due to a higher radiometric resolution and lower interference between vegetation and altered areas. As the spectral bandwidth of ETM+ band 7 covers absorption feature of propylitic alteration, better mapping of propylitic alterations is achieved using ETM+ data.     

Flow dynamics at the origin of thin clayey sand lacustrine turbidites: Examples from Lake Hazar,Turkey

Turbidity currents and their deposits can be investigated using several methods, i.e. direct monitoring, physical and numerical modelling, sediment cores and outcrops. The present study focused on thin clayey sand turbidites found in Lake Hazar (Turkey) occurring in eleven clusters of closely spaced thin beds. Depositional processes and sources for three of those eleven clusters are studied at three coring sites. Bathymetrical data and seismic reflection profiles are used to understand the specific geomorphology of each site. X‐ray, thin sections and CT scan imagery combined with grain‐size, geochemical and mineralogical measurements on the cores allow characterization of the turbidites. Turbidites included in each cluster were produced by remobilization of surficial slope sediment, a process identified in very few studies worldwide. Three types of turbidites are distinguished and compared with deposits obtained in flume studies published in the literature. Type 1 is made of an ungraded clayey silt layer issued from a cohesive flow. Type 2 is composed of a partially graded clayey sand layer overlain by a mud cap, attributed to a transitional flow. Type 3 corresponds to a graded clayey sand layer overlain by a mud cap issued from a turbulence‐dominated flow. While the published experimental studies show that turbulence is damped by cohesion for low clay content, type 3 deposits of this study show evidence for a turbulence‐dominated mechanism despite their high clay content. This divergence may in part relate to input variables, such as water chemistry and clay mineralogy, that are not routinely considered in experimental studies. Furthermore, the large sedimentological variety observed in the turbidites from one coring site to another is related to the evolution of a sediment flow within a field‐scale basin made of a complex physiography that cannot be tackled by flume experiments.     

<Emphasis Type="Italic">Spartina alterniflora</Emphasis> Biomass Allocation and Temperature: Implications for Salt Marsh Persistence with Sea-Level Rise

To predict the impacts of climate change, a better understanding is needed of the foundation species that build and maintain biogenic ecosystems. Spartina alterniflora Loisel (smooth cordgrass) is the dominant salt marsh-building plant along the US Atlantic coast. It maintains salt marsh elevation relative to sea level by the accumulation of aboveground biomass, which promotes sediment deposition and belowground biomass, which accretes as peat. Peat accumulation is particularly important in elevation maintenance at high latitudes where sediment supply tends to be limited. Latitudinal variation in S. alterniflora growth was quantified in eight salt marshes from Massachusetts to South Carolina. The hypothesis that allocation to aboveground and belowground biomass is phenotypically plastic was tested with transplant experiments among a subset of salt marshes along this gradient. Reciprocal transplants revealed that northern S. alterniflora decreased allocation to belowground biomass when grown in the south. Some northern plants also died when moved south, suggesting that northern S. alterniflora may be stressed by future warming. Southern plants that were moved north showed phenotypic plasticity in biomass allocation, but no mortality. Belowground biomass also decomposed more quickly in southern marshes. Our results suggest that warming will lead northern S. alterniflora to decrease belowground allocation and that belowground biomass will decompose more quickly, thus decreasing peat accumulation. Gradual temperature increases may allow for adaptation and acclimation, but our results suggest that warming will lower the ability of salt marshes to withstand sea-level rise.     

Agent-based tsunami evacuation modeling of unplanned network disruptions for evidence-driven resource allocation and retrofitting strategies

The constant threat from landslides in the northeastern part of Istria, Croatia, calls for the need to apply accurate and reliable methods in landslide hazard assessment in order to prevent landslide damage and to set an early warning system if necessary. Furthermore, landslide susceptibility and hazard assessment enable optimal area management and regional urban planning. The study area is in the northeastern and central part of the Istrian Peninsula, well known as an area of frequent, small and shallow slope instability phenomena. Landslide susceptibility assessment in the area around the city of Buzet was performed using a deterministic landslide susceptibility model in the LS-RAPID software. LS-RAPID was developed to analyze stability at one single location, but the performed analysis has shown that LS-RAPID can be used as a powerful tool in landslide susceptibility and hazard assessment on regional scale. The objective of this paper is to establish the influence of the runout potential on the enlargement of the landslide-susceptible zones, due to expansion of the failure area around the initial failure zone. Performed analysis of rainfall return periods shows the frequency of landslide occurrence and provides the possible correlation with the time component of landslide hazard in the area.     

Rethinking communication in risk interpretation and action

We have studied the attenuation characteristics of eastern Himalaya and southern Tibet by using local earthquake data set that consists of 123 well-located events, recorded by the Himalayan Nepal Tibet Seismic Experiment operated during 2001–2003. We have used single backscattering model to calculate frequency-dependent values of coda Q (\(Q_\mathrm{c}\)). The estimation of \(Q_\mathrm{c}\) is made at central frequencies 2, 4, 8 and 12 Hz through five lapse time windows from 10 to 50 s starting at double the travel time of the S-wave. The observed \(Q_\mathrm{c}\) is found to be strongly frequency-dependent and follows a similar trend as observed in other tectonically active parts of the Himalaya. The trend of variation of \(Q_\mathrm{c}\) with lapse time and the corresponding apparent depths is also studied. Increase in \(Q_\mathrm{c}\) values with the lapse time suggests that the deeper part of the study region is less heterogeneous than the shallower part. The observed values of \(Q_0\) (\(Q_\mathrm{c}\) at 1 Hz) and frequency parameter n indicate that the medium beneath the study area is highly heterogeneous and tectonically very active. A regionalization of the estimated \(Q_0\) is carried out, and a contour map is prepared for the whole region. Some segments of Lesser Himalaya and Sub-Himalaya exhibit very low \(Q_0\) , while the whole Tethyan Himalaya and some parts of Greater Himalaya are characterized by low \(Q_0\) values. Our results are comparable with those obtained from tectonically active regions in the world.     

Community vulnerability to hazards: introducing local expert knowledge into the equation

The accuracies of three different evolutionary artificial neural network (ANN) approaches, ANN with genetic algorithm (ANN-GA), ANN with particle swarm optimization (ANN-PSO) and ANN with imperialist competitive algorithm (ANN-ICA), were compared in estimating groundwater levels (GWL) based on precipitation, evaporation and previous GWL data. The input combinations determined using auto-, partial auto- and cross-correlation analyses and tried for each model are: (i) GWL _t?1 and GWL _t?2; (ii) GWL _t?1, GWL _t?2 and P _t ; (iii) GWL _t?1, GWL _t?2 and E _t ; (iv) GWL _t?1, GWL _t?2, P _t and E _t ; (v) GWL _t?1, GWL _t?2 and P _t?1 where GWL _t , P _t and E _t indicate the GWL, precipitation and evaporation at time t, individually. The optimal ANN-GA, ANN-PSO and ANN-ICA models were obtained by trying various control parameters. The best accuracies of the ANN-GA, ANN-PSO and ANN-ICA models were obtained from input combination (i). The mean square error accuracies of the ANN-GA and ANN-ICA models were increased by 165 and 124% using ANN-PSO model. The results indicated that the ANN-PSO model performed better than the other models in modeling monthly groundwater levels.