High-resolution near-infrared observations of Herbig–Haro flows – II. Echelle spectroscopy     

Christopher J. Davis  Aaron Berndsen  Michael D. Smith  Antonio Chrysostomou  Jason Hobson 《Monthly notices of the Royal Astronomical Society》2000,314(2):241-255

  相似文献   

Evidence for different scaling of earthquake source parameters for large earthquakes depending on faulting mechanism   总被引：2，自引：0，他引：2  

Christian Stock  Euan G. C. Smith 《Geophysical Journal International》2000,143(1):157-162

Scaling relationships between seismic moment, rupture length, and rupture width have been examined. For this purpose, the data from several previous studies have been merged into a database containing more than 550 events. For large earthquakes, a dependence of scaling on faulting mechanism has been found. Whereas small and large dip-slip earthquakes scale in the same way, the self-similarity of earthquakes breaks down for large strike-slip events. Furthermore, no significant differences in scaling could be found between normal and reverse earthquakes and between earthquakes from different regions. Since the thickness of the seismogenic layer limits fault widths, most strike-slip earthquakes are limited to rupture widths of between 15 and 30 km while the rupture length is not limited. The aspect ratio of dip-slip earthquakes is similar for all earthquake sizes. Hence, the limitation in rupture width seems to control the maximum possible rupture length for these events. The different behaviour of strike-slip and dip-slip earthquakes can be explained by rupture dynamics and geological fault growth. If faults are segmented, with the thickness of the seismogenic layer controlling the length of each segment, strike-slip earthquakes might rupture connected segments more easily than dip-slip events, and thus could produce longer ruptures than dip-slip events of the same width  相似文献   

Intraplate volcanism influenced by distal subduction tectonics at Jeju Island,Republic of Korea     

Marco Brenna  Shane J. Cronin  Gábor Kereszturi  Young Kwan Sohn  Ian E. M. Smith  Jan Wijbrans 《Bulletin of Volcanology》2015,77(1):1-16

  相似文献   

Cross‐cutting moraines reveal evidence for North Atlantic influence on glaciers in the tropical Andes     

Jacqueline A. Smith  Donald T. Rodbell 《第四纪科学杂志》2010,25(3):243-248

Surface exposure dating of boulders on an exceptionally well‐preserved sequence of moraines in the Peruvian Andes reveals the most detailed record of glaciation heretofore recognised in the region. The high degree of moraine preservation resulted from dramatic changes in the flow path of piedmont palaeoglaciers at the southern end of the Cordillera Blanca (10° 00′ S, 77° 16′ W), which, in turn, generated a series of cross‐cutting moraines. Sixty ¹⁰Be surface exposure ages indicate at least four episodes of palaeoglacier stabilisation (>65, ca. 65, ca. 32 and ca. 18–15 ka) and several minor advances or stillstands on the western side of the Nevado Jeulla Rajo massif. The absence of ages close to the global Last Glacial Maximum (ca. 21 ka) suggests that if an advance culminated at that time any resulting moraines were subsequently overridden. The timing of expanded ice cover in the central Peruvian Andes correlates broadly with the timing of massive iceberg discharge (Heinrich) events in the North Atlantic Ocean, suggesting a possible causal connection between southward migration of the Intertropical Convergence Zone during Heinrich events and a resultant increase in precipitation in the tropical Andes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Hunter‐gatherer response to late Holocene climatic variability in northern and central Australia     

Alan N. Williams  Sean Ulm  Ian D. Goodwin  Mike Smith 《第四纪科学杂志》2010,25(6):831-838

Sum probability analysis of 1275 radiometric ages from 608 archaeological sites across northern and central Australia demonstrates a changing archaeological signature that can be closely correlated with climate variability over the last 2 ka. Results reveal a marked increase in archaeological records across northern and central Australia over the last 2 ka, with notable declines in western and northern Australia between ca. AD 700 and 1000 and post‐AD 1500 – two periods broadly coeval with the Medieval Climatic Anomaly and the Little Ice Age as they have been documented in the Asia–Pacific region. Latitudinal and longitudinal analysis of the dataset suggests the increase in archaeological footprint was continent wide, while the declines were greatest from 9 to 20° S, 110 to 135° E and 143 to 150° E. The change in the archaeological data suggests that, combined with an increase in population over the late Holocene, a disruption or reorganisation of pre‐European resource systems occurred across Australia between ca. AD 700 and 1000 and post‐AD 1500. These archaeological responses can be broadly correlated with transitions of the El Niño–Southern Oscillation (ENSO) mean state on a multi‐decadal to centennial timescale. The latter involve a shift towards the La Niña‐like mean state with wetter conditions in the Australian region between AD 700 and 1150. A transition period in ENSO mean state occurred across Australia during AD 1150–1300, with persistent El Niño‐like and drier conditions to ca. AD 1500, and increasing ENSO variability post‐AD 1500 to the present. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Early Devensian (MIS 5d–5b) occupation at Dartford,southeast England     

Francis F. Wenban‐Smith  Martin R. Bates  Jean‐Luc Schwenninger 《第四纪科学杂志》2010,25(8):1193-1199

A deeply buried horizon containing mint‐condition flint artefacts was discovered in 2006 during archaeological investigations in advance of major roadworks near Dartford, Kent, in southeast England. The context of the artefacts and the freshness of their condition suggest this horizon represents a buried occupation surface. Optically stimulated luminescence dating places this horizon in the period Marine Isotope Stage 5d–5b, early in the British Devensian glaciation. This paper describes details of the artefacts, their context and dates, and outlines how this apparent occupation fits in with the wider pattern of Neanderthal settlement in Britain and northwest Europe in the later Pleistocene. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Holocene relative sea‐level changes in Harris,Outer Hebrides,Scotland, UK     

Jason T. Jordan  David E. Smith  Sue Dawson  Alastair G. Dawson 《第四纪科学杂志》2010,25(2):115-134

Evidence for relative sea‐level changes during the middle and late Holocene is examined from two locations on the Atlantic coast of Harris, Outer Hebrides, Scotland, using morphological mapping and survey, stratigraphical, grain size and diatom analysis, and radiocarbon dating. The earliest event identified is a marine flood, which occurred after 7982–8348 cal. a (7370 ± 80 ¹⁴C a) BP, when the sea crossed a threshold lying at ?0.08 m Ordnance Datum Newlyn (OD) (?2.17 m mean high water springs (MHWS)) before withdrawing. This could have been due to a storm or to the Holocene Storegga Slide tsunami. By 6407–6122 cal. a (5500 ± 60 ¹⁴C a) BP, relative sea levels had begun to fall from a sandflat surface with an indicated MHWS level of between 0.08 and ?1.96 m (?2.01 to ?4.05 m). This fall reached between ?0.30 and ?2.35 m (?2.39 to ?4.44 m) after 5841–5050 cal. a (4760 ± 130 ¹⁴C a) BP, but was succeeded by a relative sea‐level rise which reached between 0.54 and ?1.57 m (?1.55 to ?3.66 m) by 5450–4861 cal. a (4500 ± 100 ¹⁴C a) BP. This rise continued, possibly with an interruption, until a second sandflat surface was reached between 2.34 and ?0.26 m (0.25 to ?2.35 m) between 2952–3375 cal. a (3000 ± 80 ¹⁴C a) and 1948–2325 cal. a (2130 ± 70 ¹⁴C a) BP, before present levels were reached. The regressive episode from the earliest sandflat is correlated with the abandonment of the Main Postglacial Shoreline. It is maintained that the fluctuations in relative sea level recorded can be correlated with similar events elsewhere on the periphery of the glacio‐isostatic centre and may therefore reflect secular changes in nearshore sea surface levels. Despite published evidence from trim lines of differential ice sheet loading across the area, no evidence of variations in uplift between the locations concerned could be found. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Anthony Dosseto, Simon P. Turner, James A. Van Orman: timescales of magmatic processes from core to atmosphere     

Ian E. M. Smith 《Bulletin of Volcanology》2011,73(7):933-934

  相似文献   

Late Holocene fluctuations of Quelccaya Ice Cap,Peru, registered by nearby lake sediments          下载免费PDF全文

Justin S. Stroup  Meredith A. Kelly  Thomas V. Lowell  Colby A. Smith  Samuel A. Beal  Joshua D. Landis  Pedro M. Tapia 《第四纪科学杂志》2015,30(8):830-840

  相似文献   

Hormone loads exported by a tile‐drained agroecosystem receiving animal wastes          下载免费PDF全文

Heather E. Gall  Stephen A. Sassman  Byron Jenkinson  Linda S. Lee  Chad T. Jafvert 《水文研究》2014,28(3):1318-1328

Little is known regarding hormone export from tile‐drained agricultural fields despite the widespread presence of tile drains in the Midwestern United States. By intensively measuring water flow rates and hormone concentrations in four subsurface tile drains and three receiving ditches at a working Midwest farm, hormone fluxes and loads from the tile‐drained fields were quantified. Before and during the 17‐month study period (January 2009 – May 2010), the associated farm fields received various animal waste applications (beef, dairy, poultry, sheep, and swine). Hormones monitored included the estrogens17β‐ and 17α‐estradiol, estrone, and estriol; the natural androgens testosterone, and androstenedione; and the synthetic androgens 17β‐ and 17α‐trenbolone, and trendione. Hormone loads measured in the ditches for three drainage areas during the entire 17‐month study period were in ranges of 16–58 mg/ha for total estrogens, 6.8–19 mg/ha for natural androgens, and 4.2–44 mg/ha for synthetic androgens. Because higher hormone concentrations generally occurred during discrete periods of increased flow, high flow rates often were associated with a disproportionately high hormone flux. For example, 80% of total estrogens and natural androgens exported into the ditches occurred during only 9–26% of the study period, coinciding with the most significant storm events. In addition, hormone fluxes were highest during storm events that occurred shortly after animal waste applications. Therefore, to effectively reduce hormone loads exported to downstream aquatic ecosystems in the absence of any application reduction, the short periods during which high‐flow events occur must be targeted. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献