Apparent polar wander of the mean-lithosphere reference frame     

Richard G. Gordon  Roy A. Livermore 《Geophysical Journal International》1987,91(3):1049-1057

Apparent polar wander in the mean-lithosphere (= no-net-rotation = no-net-torque uniform drag) reference frame is compared with apparent polar wander in the hotspot reference frame over the past 100 Myr. Palaeo-magnetic poles and plate rotations previously used to determine an apparent polar wander path for the hotspot reference frame are here used to determine an apparent polar wander path in the mean-lithosphere reference frame. We find that the two paths are similar, especially for Late Cretaceous time, when a 10°–20° shift of the pole occurred. To first-order the hotspots and lithosphere (as a whole) moved in unison relative to the palaeomagnetic axis during Late Cretaceous time. A non-dipole field explanation for the apparent shift can probably be excluded. However, either motion of the time-averaged geomagnetic axis relative to the spin axis or polar wandering could have caused this shift, the latter being the more likely explanation.  相似文献   

A reconfigurable real-time interpolation beamformer     

Da Sylva  P. Menard  P. Roy  D. 《Oceanic Engineering, IEEE Journal of》1986,11(1):123-126

This paper describes an architecture for a compact real-time time-delay sonar beamformer. The design is based on a time-domain interpolation concept, and includes shading, interpolation, and time-delay functions for up to 64 sensor data inputs. A one card per beam configuration has been achieved. The digital interpolation technique used improves the effective sampling rate by a factor of 128. The beamformer design features 16-bit arithmetic precision, up to approximately a 5-kHz sampling rate for each of the 64 sensor input channels, and adaptability to any type of array, e.g., linear, circular, or arrays with nonequal interelement spacings. A 31-beam beamformer system, performing more than 620-million arithmetic operations a second, is discussed.  相似文献   

Revised marine reservoir offset (ΔR) values for molluscs and marine mammals from Arctic North America     

Anna J. Pieńkowski  Roy D. Coulthard  Mark F. A. Furze 《Boreas: An International Journal of Quaternary Research》2023,52(2):145-167

Appropriate marine–terrestrial reservoir offset (ΔR) values are essential for accurate calibration of marine radiocarbon dates. However, ΔR values are only valid for the specific calibration curve that their calculation is based on. Here, we present revised ΔR values for the Marine20 calibration curve from Arctic North America, based on previously published ¹⁴C dates on pre-bomb live-collected marine molluscs (n = 124) and cetaceans (beluga whales; tooth dentine; n = 12), and bowhead whale–driftwood age comparisons from the same glacio-isostatically uplifted shorelines (n = 18). Molluscan-based ΔR are: Chukchi/Beaufort sea coasts, 265±116 ¹⁴C years; NW Canadian Arctic Archipelago, 188±91 ¹⁴C years; NE Baffin Island, 81±18 ¹⁴C years; SE Baffin Island, 14±58 ¹⁴C years; Hudson Strait, −73±64 ¹⁴C years; Ungava Bay, 0±86 ¹⁴C years; Foxe Basin, 175±89 ¹⁴C years; Hudson Bay, −21±72 ¹⁴C years; James Bay, 209±114 ¹⁴C years; West Greenland, −93±111 ¹⁴C years. Species-specific marine mammal ΔR terms are 107±59 ¹⁴C years for beluga and 24±58 ¹⁴C years for bowheads. Our revised ΔR values are applicable for as long as the same broad oceanographic conditions (circulation, ventilation) have persisted, i.e. through the Holocene. While molluscan values are applicable to other marine carbonate (e.g. foraminifera), cetacean ΔR are valid only for the species they were calculated for and should not be applied to other marine mammals. Importantly, the ΔR terms calculated here are only valid for Marine20 and should not be used with earlier or later calibration curves.  相似文献   

Continual long-term monitoring of methane in wells above the Utica Shale using total dissolved gas pressure probes     

Roy  James W.  Bordeleau  Genevi&#;ve  Rivard  Christine  Ryan  M. Cathryn  Malet  Xavier  Brown  Susan J.  Tremblay  Vincent 《Hydrogeology Journal》2022,30(3):1005-1019

Hydrogeology Journal - Monitoring of dissolved methane concentrations in groundwater is required to identify impacts from oil and gas development and to understand temporal variability under...  相似文献   

Reactivating Balia Nala landslide,Nainital, India—a disaster in waiting     

Roy  Priyom  Jain  Nirmala  Martha  Tapas R.  Kumar  K. Vinod 《Landslides》2022,19(6):1531-1535

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Seismic source characteristics in Kachchh and Saurashtra regions of Western India: <Emphasis Type="Italic">b</Emphasis>-value and fractal dimension mapping of aftershock sequences     

A. P. Singh  Indrajit G. Roy  Santosh Kumar  J. R. Kayal 《Natural Hazards》2015,75(1):33-55

Seismic source characteristics in the Kachchh rift basin and Saurashtra horst tectonic blocks in the stable continental region (SCR) of western peninsular India are studied using the earthquake catalog data for the period 2006–2011 recorded by a 52-station broadband seismic network known as Gujarat State Network (GSNet) running by Institute of Seismological Research (ISR), Gujarat. These data are mainly the aftershock sequences of three mainshocks, the 2001 Bhuj earthquake (M _w 7.7) in the Kachchh rift basin, and the 2007 and 2011 Talala earthquakes (M _w ≥ 5.0) in the Saurashtra horst. Two important seismological parameters, the frequency–magnitude relation (b-value) and the fractal correlation dimension (D _c) of the hypocenters, are estimated. The b-value and the D _c maps indicate a difference in seismic characteristics of these two tectonic regions. The average b-value in Kachchh region is 1.2 ± 0.05 and that in the Saurashtra region 0.7 ± 0.04. The average D _c in Kachchh is 2.64 ± 0.01 and in Saurashtra 2.46 ± 0.01. The hypocenters in Kachchh rift basin cluster at a depth range 20–35 km and that in Saurashtra at 5–10 km. The b-value and D _c cross sections image the seismogenic structures that shed new light on seismotectonics of these two tectonic regions. The mainshock sources at depth are identified as lower b-value or stressed zones at the fault end. Crustal heterogeneities are well reflected in the maps as well as in the cross sections. We also find a positive correlation between b- and D _c-values in both the tectonic regions.  相似文献   

Progressive failure leading to the 3 December 2013 rockfall at Puigcercós scarp (Catalonia,Spain)   总被引：1，自引：1，他引：0  

Manuel?J.?RoyánEmail author  Antonio?Abellán  Joan?Manuel?Vilaplana 《Landslides》2015,12(3):585-595

A detailed analysis of the pre-failure behavior of the 3 December 2013 rockfall (1,012 m³) occurred on Puigcercós pilot study area (Catalonia, Spain) is presented. The exact date of failure was obtained based on a photographic monitoring performed every 4 h. The long-term monitoring (2,217 days) of the rock slope carried out by a Terrestrial LiDAR allowed the early detection of both pre-failure deformation and precursory rockfalls preceding the final failure. By means of the analysis of the pre-failure deformation, four different deformed areas were detected and the tertiary creep phase was observed in three of them. An attempt to predict the time to failure was performed using the Fukuzono’s (1985) method. Furthermore, the temporal evolution of the precursory rockfalls occurred in those four areas during the progressive failure showed a close resemblance with the exponential pattern of the cumulated displacements at tertiary creep stage. Finally, the study of the meteorological conditions did not show any single triggering factor associated with the final failure. Reversely, the increase in the occurrence of precursory rockfalls on several areas of the slope together with the observed acceleration on the deformation pattern reinforce the role of a progressive degradation of the stability conditions, which ultimately leaded to the 3 December rockfall event.  相似文献   

Effects of bedrock anisotropy on hillslope failure in the Darjeeling-Sikkim Himalaya: an insight from physical and numerical models     

Sujit Roy  Amiya Baruah  Santanu Misra  Nibir Mandal 《Landslides》2015,12(5):927-941

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Convection-permitting regional climate simulation of warm-season precipitation over Eastern China     

Yun  Yuxing  Liu  Changhai  Luo  Yali  Liang  Xudong  Huang  Ling  Chen  Fei  Rasmmusen  Roy 《Climate Dynamics》2020,54(3):1469-1489

Climate Dynamics - Convection-permitting regional climate models have been shown to improve precipitation simulation in many aspects, such as the diurnal cycle, precipitation frequency, intensity...  相似文献   

Response of surface water chemistry to reduced levels of acid precipitation: comparison of trends in two regions of New York,USA     

Douglas A. Burns  Michael R. McHale  Charles T. Driscoll  Karen M. Roy 《水文研究》2006,20(7):1611-1627

In light of recent reductions in sulphur (S) and nitrogen (N) emissions mandated by Title IV of the Clean Air Act Amendments of 1990, temporal trends and trend coherence in precipitation (1984–2001 and 1992–2001) and surface water chemistry (1992–2001) were determined in two of the most acid‐sensitive regions of North America, i.e. the Catskill and Adirondack Mountains of New York. Precipitation chemistry data from six sites located near these regions showed decreasing sulphate (SO₄^2?), nitrate (NO₃^?), and base cation (C_B) concentrations and increasing pH during 1984–2001, but few significant trends during 1992–2001. Data from five Catskill streams and 12 Adirondack lakes showed decreasing trends in SO₄^2? concentrations at all sites, and decreasing trends in NO₃^?, C_B, and H⁺ concentrations and increasing trends in dissolved organic carbon at most sites. In contrast, acid‐neutralizing capacity (ANC) increased significantly at only about half the Adirondack lakes and in one of the Catskill streams. Flow correction prior to trend analysis did not change any trend directions and had little effect on SO₄^2? trends, but it caused several significant non‐flow‐corrected trends in NO₃^? and ANC to become non‐significant, suggesting that trend results for flow‐sensitive constituents are affected by flow‐related climate variation. SO₄^2? concentrations showed high temporal coherence in precipitation, surface waters, and in precipitation–surface water comparisons, reflecting a strong link between S emissions, precipitation SO₄^2? concentrations, and the processes that affect S cycling within these regions. NO₃^? and H⁺ concentrations and ANC generally showed weak coherence, especially in surface waters and in precipitation–surface water comparisons, indicating that variation in local‐scale processes driven by factors such as climate are affecting trends in acid–base chemistry in these two regions. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献