Time variant analysis of geomagnetic signals describes the volcanic activity of Mt. Etna between early 2000 and late 2002

Volcanomagnetic anomalies have been mostly observed during strong eruptions. Our aim is to improve the geomagnetic data analysis to evidence the anomalies occurring in a larger time span, especially in the phases preceding the eruptive events. We developed a time variant statistical approach and applied it to the 2000–2002 Etna geomagnetic temporal series. It is based on an algorithm that statistically predicts the geomagnetic field at the station on the volcanic edifice by that recorded at the remote one. In such a way a number of significant changes in the time series (called statistical innovations), marking the local magnetic field change, were detected. The distribution of such statistical innovations accurately describes the Etna volcanic evolution: we note a progressive increase of the innovation occurrence as the eruptive cycles were approaching and only few and weak innovations at times between the various eruptive cycles. The significance of this analysis is further confirmed by the close agreement among the mean square prediction error, strain release and the volcanic activity behavior. On the contrary, the geomagnetic field at a single station or its difference at two stations do not have any clear correlation with other measured physical quantities. The complex pattern of the prediction error was also investigated by a multifractal analysis. We found that the Holder regularity increases with the intensification of the volcanic activity, implying that innovations tend to be less sporadic and correlated during the major volcanic phases.     

Impact of pre-stress,inhomogeneity and porosity on the propagation of Love wave

This work presents a mathematical modelling of Love wave transference through a pre-stress influenced anisotropic medium with heterogeneity between a sandy medium and an initially stressed anisotropic porous medium. Variable separation method has been induced in order to derive the frequency relation. Using appropriate boundary conditions at two interfaces, the dispersion equation has been obtained in its closed form. Possible particular cases are considered, and the corresponding results are consonant with the classical cases. Numerical computations have been employed to demonstrate the role of inhomogeneity factors, initial stresses and porosity, and are depicted by means of graphs which substantiates that those parameters immensely affect the Love wave velocity. In mineral prospecting and exploring technique in earth, the method and the results of this problem may be applicable.     

Supernova remnants, planetary nebulae and the distance to NGC 4214

We present narrow band, continuum subtracted Hα, [S ii], Hβ, [O iii] and [O ii] data taken with the Wide Field Camera 3 on the Hubble Space Telescope in the nearby dwarf starburst galaxy NGC 4214. From these images, we identify seventeen new planetary nebula candidates, and seven supernova remnant candidates. We use the observed emission line luminosity function of the planetary nebulae to establish a new velocity-independent distance to NGC 4214. We conclude that the PNLF technique gives a reddening independent distance to NGC 4214 of 3.19±0.36 Mpc, and that our current best-estimate of the distance to this galaxy ids 2.98±0.13 Mpc.     

Ediacaran fossils in Meso- and Paleoproterozoic rocks in peninsular India extend Darwin

Typically or arguably Ediacaran fossils (635 Ma to 543 Ma) are reported by several research groups from one unit of the Chhattisgarh and two units of the Vindhyan Supergroups in peninsular India. Depositional ages of the host sediments, however, are inferred to be ∼1000 Ma and ∼ 1630 Ma as determined by U-Pb dating of magmatic and detrital zircons in rhyolitic tuff (∼ porcellanite) and sandstones, provenance considerations and paleopole positions. The contradiction of absolute ages results from inferring the Ediacaran age strictly on the basis of fossils. I argue that the fossils reported from the Chhattisgarh and Vindhyan Supergroups should be considered mostly Mesoproterozoic and late Proterozoic in age. I also argue that although the Ediacaran Period records explosive diversity of preserved fossils, many forms very likely appeared much earlier with variable degrees of preservation or none at all at times, and, that their age-ranges extend to the Paleoproterozoic. I hypothesize that the rate of increase of biological diversity was lower than the rate of preservation in certain geological intervals, especially immediately after extinction events.     

Experimental investigation of gas-water relative permeability for gas-hydrate-bearing sediments from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Permeability of hydrate reservoirs found in nature is likely to be heavily influenced by the percent of the pore volume occupied by hydrates. The quantification of how hydrate saturation affects permeability is of key interest for reservoir engineering studies. In this study, an experimental setup was modified to test permeability characteristics of unconsolidated core samples containing various saturations of methane hydrates. Hydrates were formed in the unconsolidated samples using a refrigerated core holder connected to a brine and methane injection system. Studies of this type conducted to date have rarely been performed on core samples recovered from actual hydrate-bearing sedimentary sections from natural hydrate intervals. Samples from the Mount Elbert site on the Alaska North Slope (ANS) were used for this study.Relative permeability measurements using hydrate constituent components (e.g. water and methane) are not very desirable due to difficulties in preventing additional hydrate formation during displacement experiments. Relative permeability measurements performed with hydrate constituent components (e.g. water and nitrogen) can help to significantly mitigate issues with additional hydrate formation. However, unsteady state relative permeability experiments produce piston like displacement results suggesting that steady state experiments might be preferable.It was observed that as in previous work using consolidated core samples, permeability of both brine and gases was reduced in unconsolidated hydrate-bearing core samples. Experimental results show that low to moderate hydrate saturations (1.5 to 36%) can significantly reduce permeability of porous media. These saturations, in fact, are lower than hydrate saturations observed in the natural hydrate systems at Mount Elbert.     

A high-resolution seismic catalog for the 2021 MS6.4/MW6.1 Yangbi earthquake sequence,Yunnan, China: Application of AI picker and matched filter

We present a high-resolution seismic catalog for the 2021 M_S6.4/M_W6.1 Yangbi sequence. The catalog has a time range of 2021-05-01 to 2021-05-28, and contains ~8,000 well located events. It captures the features of the whole foreshock sequence and the early aftershocks. We designed a detection strategy incorporating both an artificial intelligent (AI) picker and a matched filter algorithm. Here, we adopt a hybrid AI method incorporating convolutional and recurrent neural network (CNN & RNN) for event detection and phase picking respectively (i.e. CERP), a light-weight AI picker that can be trained with small volume of data. CERP is first trained with detections from a STA/LTA and Kurtosis-based method called PAL, and then construct a rather complete template set of ~4,000 events. Finally, the matched filter algorithm MESS augments the initial detections and measures differential travel times with cross-correlation, which finally results in precise relocation. This process gives 9,026 detections, among which 7,943 events can be well relocated. The catalog shows as expected power-law distribution of frequency magnitude and reveals detailed pattern of seismicity evolution. The main features are: (1) the foreshock sequence images simple fault geometry with consistent strike, but also show a variable event depth along strike; (2) the mainshock ruptures the same fault of the foreshock sequence and activate conjugate faults further to the southeast; (3) complex seismicity are developed in the post-seismic period, indicating complex triggering mechanisms. Thus, our catalog provides a reliable basis for further investigations, such as b-value studies, rupture process, and triggering relations.     

Validation of Indian National DEM from Cartosat-1 Data

CartoDEM is an Indian National DEM generated from Cartosat-1 stereo data. Cartosat-1, launched in May, 2005, is an along track (aft ?5°, Fore +26°) stereo with 2.5 m GSD, give base-height ratio of 0.63 with 27 km swath. The operational procedure of DEM generation comprises stereo strip triangulation of 500?×?27 km segment with 10 m posting along with 2.5 m resolution ortho image and free—access posting of 30 m has been made available (bhuvan.nrsc.gov.in). A multi approach evaluation of CartoDEM comprising (a) absolute accuracy with respect to ground control points for two sites namely Jagatsinghpur -flat and Dharamshala- hilly; second site i.e. Alwar-plain and hilly with high resolution aerial DEM, (b) relative difference between SRTM and ASTERDEM (c) absolute accuracy with ICESat GLAS for two sites namely Jagatsinghpur-plain and Netravathi river, Western Ghats-hilly (d) relative comparison of drainage delineation with respect to ASTERDEM is reported here. The absolute height accuracy in flat terrain was 4.7 m with horizontal accuracy of 7.3 m, while in hilly terrain it was 7 m height with a horizontal accuracy of 14 m. While comparison with ICESat GLAS data absolute height difference of plain and hilly was 5.2 m and 7.9 m respectively. When compared to SRTM over Indian landmass, 90 % of pixels reported were within ±8 m difference. The drainage delineation shows better accuracy and clear demarcation of catchment ridgeline and more reliable flow-path prediction in comparison with ASTER. The results qualify Indian DEM for using it operationally which is equivalent and better than the other publicly available DEMs like SRTM and ASTERDEM.     

Propagation of Love wave in fiber‐reinforced medium lying over an initially stressed orthotropic half‐space

In this paper, the propagation of Love waves in a fiber‐reinforced layered medium lying over an elastic orthotropic half‐space under initial stress has been investigated. We have obtained the velocity equations for Love wave in this media. It is observed that propagation of Love wave is influenced by reinforced parameters and initial stressed parameter. The velocity of Love wave has been computed for three different cases. Our computed equation of Love wave coincides with the standard equation of Love wave for the case of homogeneous layer and homogeneous half‐space (AEH Love, 1911). To study the effect of reinforced and initial stressed parameters, we have computed the numerical values for phase velocity and plotted in several figures. It is observed that the phase velocity decreases with the increases of reinforced parameters and initial stressed parameter. Using MATLAB software, GUI has been developed to generalize the effect of various parameters. Copyright © 2014 John Wiley & Sons, Ltd.     

Latitudinal trends in morphological characteristics of <Emphasis Type="Italic">Neogloboquadrina pachyderma</Emphasis> (Ehrenberg) along a north–south transect in the south-western Indian Ocean

A total of 25 surficial sediment samples (Peterson grab, gravity and piston cores), collected during the Pilot Expedition to Southern Ocean (PESO) 2004 cruises 199C and 200 onboard the ORV Sagar Kanya along a N–S transect between 9.69°N and 55.01°S, and 80 and 40°E in the Indian Ocean sector of the Southern Ocean (SW Indian Ocean), have been investigated for various morphological features—test size, mean proloculus size and coiling direction (dextral/sinistral forms)—of the planktic indicator species Neogloboquadrina pachyderma (Ehrenberg). The results show that the coiling directions co-vary with temperature and salinity, the abundances of sinistrally coiled forms increasing towards higher latitudes (south of 40°S), whereas dextrally coiled forms show a reverse trend. Similarly, overall test and proloculus sizes depend largely on the physicochemical properties (salinity, temperature, nutrients, calcium saturation) of the ambient water masses. These observations suggest that, particularly at the boundaries between different water masses, variations in morphological features of N. pachyderma can meaningfully be used to reconstruct paleoceanographic conditions from Indian Ocean sediments.     

Higher dimensional cosmological model with a time-dependent equation of state

A homogeneous cosmological model in higher dimension is obtained assuming a timedependent equation of state. It is observed that as usual 3-D space expands, extra space (space belonging to the other dimensions) reduces with time, thus exhibiting the desired feature of dimensional reduction. The dynamical behavior of the model is examined and it is noted that with a decrease in extra space the observable 3-D space entropy increase, thus accounting for the large value of entropy observable at present.