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1.
Joëlle Gergis Ailie Jane Eyre Gallant Karl Braganza David John Karoly Kathryn Allen Louise Cullen Rosanne D’Arrigo Ian Goodwin Pauline Grierson Shayne McGregor 《Climatic change》2012,111(3-4):923-944
This study presents the first multi-proxy reconstruction of rainfall variability from the mid-latitude region of south-eastern Australia (SEA). A skilful rainfall reconstruction for the 1783–1988 period was possible using twelve annually-resolved palaeoclimate records from the Australasian region. An innovative Monte Carlo calibration and verification technique is introduced to provide the robust uncertainty estimates needed for reliable climate reconstructions. Our ensemble median reconstruction captures 33% of inter-annual and 72% of decadal variations in instrumental SEA rainfall observations. We investigate the stability of regional SEA rainfall with large-scale circulation associated with El Niño–Southern Oscillation (ENSO) and the Inter-decadal Pacific Oscillation (IPO) over the past 206 years. We find evidence for a robust relationship with high SEA rainfall, ENSO and the IPO over the 1840–1988 period. These relationships break down in the late 18th–early 19th century, coinciding with a known period of equatorial Pacific Sea Surface Temperature (SST) cooling during one of the most severe periods of the Little Ice Age. In comparison to a markedly wetter late 18th/early 19th century containing 75% of sustained wet years, 70% of all reconstructed sustained dry years in SEA occur during the 20th century. In the context of the rainfall estimates introduced here, there is a 97.1% probability that the decadal rainfall anomaly recorded during the 1998–2008 ‘Big Dry’ is the worst experienced since the first European settlement of Australia. 相似文献
2.
Keyan Fang Nicole Davi Xiaohua Gou Fahu Chen Edward Cook Jinbao Li Rosanne D’Arrigo 《Climate Dynamics》2010,35(6):941-951
Spatial reconstructions of drought for central High Asia based on a tree-ring network are presented. Drought patterns for
central High Asia are classified into western and eastern modes of variability. Tree-ring based reconstructions of the Palmer
drought severity index (PDSI) are presented for both the western central High Asia drought mode (1587–2005), and for the eastern
central High Asia mode (1660–2005). Both reconstructions, generated using a principal component regression method, show an
increased variability in recent decades. The wettest epoch for both reconstructions occurred from the 1940s to the 1950s.
The most extreme reconstructed drought for western central High Asia was from the 1640s to the 1650s, coinciding with the
collapse of the Chinese Ming Dynasty. The eastern central High Asia reconstruction has shown a distinct tendency towards drier
conditions since the 1980s. Our spatial reconstructions agree well with previous reconstructions that fall within each mode,
while there is no significant correlation between the two spatial reconstructions. 相似文献
3.
A. Caserta F. Bellucci G. Cultrera S. Donati F. Marra G. Mele B. Palombo A. Rovelli 《Journal of Seismology》2000,4(4):555-565
During the ML = 5.6 and 5.8 earthquakes occurredin central Italy on 26 September 1997 the historiccentre of Nocera Umbra, lying on top of a 120 m highhill, was diffusely damaged (VII-VIII degrees of MCSintensity). Some recently built houses in the modernpart of the town suffered an even higher level ofdamage. A temporary seismic array was deployed toinvestigate a possible correlation between localamplifications of ground motion in this area and theobserved pattern of damage. After a geologic andmacroseismic survey, eight sites were selected asrepresentative of different local conditions, such astopographic irregularities, sharp hard-to-softlithology transitions, alluvium-filled valleys, andboth undisturbed and deformed rocks.Horizontal-to-vertical spectral ratios for bothmicrotremor and earthquake recordings, as well asspectral ratios referred to undisturbed rock sites,were used to quantify local variations of groundmotion. In spite of the diffuse damage in the historiccentre of Nocera Umbra, a small amplification isobserved at the stations on the hill's top. Thissuggests that the higher vulnerability of the ancientbuildings mainly accounts for the diffuse damage inthat part of the town. In the frequency band ofengineering interest (1 to 10 Hz) the largestamplifications of ground motion are found at softsites: in the Topino river valley, where many episodesof severe structural damage occurred, spectralamplification is significant over a broad frequencyband ranging from 2 Hz to more than 20 Hz. Inparticular, in the central part of the valley highamplification (> 4) is found from 3 to 10 Hz,reaching a maximum of 20 around 4 Hz. At the edge ofthe valley, close to the soil-to-rock transition,amplification is as large as 10 in a frequency bandranging from 4 to more than 20 Hz. A significantamplification (by a factor of 10 around 10 Hz) isobserved also at one of the rock sites, possibly dueto the presence of a cataclastic zone related to theactivity of a regional fault that altered themechanical properties of the rock. 相似文献
4.
M. Bouchon S. Gaffet C. Cornou M. Dietrich J.P. Glot F. Courboulex A. Caserta G. Cultrera F. Marra R. Guiguet 《Journal of Seismology》2000,4(4):517-523
We found extensive evidence that the vertical ground accelerations produced during the largest shock (M = 6.0) of the 1997 Umbria-Marche earthquake sequence exceeded 1g in two areas close to the heavily-damaged villages of Annifo and Colle Croce. This evidence comes from the striking observation of thousands of freshly fractured and broken rocks and stones in these areas. Some of the broken stones lie isolated on soft detritic soil while others had been previously piled up, probably a long time agoto clear the fields for farming. The freshness of the cuts and fractures and the consistency of the observations for thousands of rocks and stones in these areas indicate that these rocks were thrown upwards during the earthquake, with breakage occurring at the time of impact. Ground motion calculations consistent with the static deformation inferred from GPS and interferometry data, show that the broken stones and rocks are found in the zone where the strongest shaking took place during the earthquake and that most of the shaking there was vertical. 相似文献
5.
T. Appourchaux P. Liewer M. Watt D. Alexander V. Andretta F. Auchère P. D’Arrigo J. Ayon T. Corbard S. Fineschi W. Finsterle L. Floyd G. Garbe L. Gizon D. Hassler L. Harra A. Kosovichev J. Leibacher M. Leipold N. Murphy M. Maksimovic V. Martinez-Pillet B. S. A. Matthews R. Mewaldt D. Moses J. Newmark S. Régnier W. Schmutz D. Socker D. Spadaro M. Stuttard C. Trosseille R. Ulrich M. Velli A. Vourlidas C. R. Wimmer-Schweingruber T. Zurbuchen 《Experimental Astronomy》2009,23(3):1079-1117
The POLAR Investigation of the Sun (POLARIS) mission uses a combination of a gravity assist and solar sail propulsion to place
a spacecraft in a 0.48 AU circular orbit around the Sun with an inclination of 75° with respect to solar equator. This challenging
orbit is made possible by the challenging development of solar sail propulsion. This first extended view of the high-latitude
regions of the Sun will enable crucial observations not possible from the ecliptic viewpoint or from Solar Orbiter. While
Solar Orbiter would give the first glimpse of the high latitude magnetic field and flows to probe the solar dynamo, it does
not have sufficient viewing of the polar regions to achieve POLARIS’s primary objective: determining the relation between
the magnetism and dynamics of the Sun’s polar regions and the solar cycle.
相似文献
| T. AppourchauxEmail: |
6.
G. Amelino-Camelia K. Aplin M. Arndt J. D. Barrow R. J. Bingham C. Borde P. Bouyer M. Caldwell A. M. Cruise T. Damour P. D’Arrigo H. Dittus W. Ertmer B. Foulon P. Gill G. D. Hammond J. Hough C. Jentsch U. Johann P. Jetzer H. Klein A. Lambrecht B. Lamine C. Lämmerzahl N. Lockerbie F. Loeffler J. T. Mendonca J. Mester W.-T. Ni C. Pegrum A. Peters E. Rasel S. Reynaud D. Shaul T. J. Sumner S. Theil C. Torrie P. Touboul C. Trenkel S. Vitale W. Vodel C. Wang H. Ward A. Woodgate 《Experimental Astronomy》2009,23(2):549-572
The GAUGE (GrAnd Unification and Gravity Explorer) mission proposes to use a drag-free spacecraft platform onto which a number
of experiments are attached. They are designed to address a number of key issues at the interface between gravity and unification
with the other forces of nature. The equivalence principle is to be probed with both a high-precision test using classical
macroscopic test bodies, and, to lower precision, using microscopic test bodies via cold-atom interferometry. These two equivalence
principle tests will explore string-dilaton theories and the effect of space–time fluctuations respectively. The macroscopic
test bodies will also be used for intermediate-range inverse-square law and an axion-like spin-coupling search. The microscopic
test bodies offer the prospect of extending the range of tests to also include short-range inverse-square law and spin-coupling
measurements as well as looking for evidence of quantum decoherence due to space–time fluctuations at the Planck scale. 相似文献
7.
Keyan Fang Xiaohua Gou Fahu Chen Jinbao Li Rosanne D’Arrigo Edward Cook Tao Yang Nicole Davi 《Climate Dynamics》2010,35(4):577-585
We present a Palmer Drought Severity Index reconstruction (r = 0.61, P < 0.01) from 1440 to 2007 for the southeastern Tibetan Plateau, based on tree rings of the forest fir (Abies forrestii). Persistent decadal dry intervals were found in the 1440s–1460s, 1560s–1580s, 1700s, 1770s, 1810s, 1860s and 1980s, and
the extreme wet epochs were the 1480s–1490s, 1510s–1520s, 1590s, 1610s–1630s, 1720s–1730s, 1800s, 1830s, 1870s, 1930s, 1950s
and after the 1990s. Comparisons of our record with those identified in other moisture related reconstructions for nearby
regions showed that our reconstructed droughts were relatively consistent with those found in other regions of Indochina,
suggesting similar drought regimes. Spectral peaks of 2.3–5.5 years may be indicative of ENSO activity, as also suggested
by negative correlations with SSTs in the eastern equatorial and southeastern Pacific Ocean. Significant multidecadal spectral
peaks of 29.2–40.9 and 56.8–60.2 years were identified. As indicated by the spatial correlation patterns, the decadal-scale
variability may be linked to SST variations in the northern Pacific and Atlantic Oceans. 相似文献
8.
Stéphane Gaffet Giovanna Cultrera Michel Dietrich Françoise Courboulex Fabrizio Marra Michel Bouchon Arrigo Caserta Cécile Cornou Anne Deschamps Jean-Paul Glot Robert Guiguet 《Journal of Seismology》2000,4(4):525-541
Strong site effects were observed during the two M
W 5.7 and M
W 6.0 main shocks of the Colfiorito seismic crisis which occured on September 26, 1997 in Umbria-Marche (Central Italy).The most obvious indications of these effects are the dramatic differences in damage shown by buildings of similar construction in neighboring villages.Such observations were specifically made in the Verchiano valley in the fault area, 15 km south of Colfiorito where the Verchiano village and the Colle and Camino hamlets were heavily damaged (MCS intensity IX-X) since the first main shock of 1997/09/26,while in contrast, the Curasci village located 2 km eastwards remains almost intact.In order to study the anomalous ground motion amplifications in this area, an array of 11, 3-components seismo- and accelero-meters was set up during the 1997/10/20-24 period, extending from the western side of the valley, up to the top of Mount San Salvatore, going accross the Colle and Curasci hamlets.During the experiment, 67 aftershocks enlightened the valley from the Colfiorito (10 km north) and the Sellano (6 km south) active swarms.Seismic refraction experiments were conducted at the same time in the 500 m wide, 1500 m long Verchiano valley in order to determine the thickness and main characteristics of the alluvial infilling.The main results are: (i) compared to the valley side ground motion, and for all the events, recordings in the central part of the valley (piana di Verchiano) show relative amplification of 10 with a clear lengthening of the seismogram duration by a factor of 2 – (ii) broad band relative amplification of 6–8 is also clearly identified at the top of the Mount San Salvatore overhanging the valley – (iii) any of the site effect measurements done explains by itself the strongly contrasted damage observed at Colle and Curasci: i.e. the modification of the near-field radiation pattern by interaction with the free heterogeneous surface may have induced local shadow zones that saved Curasci. 相似文献
9.
Large amplification of ground motion at rock sites within a fault zone in Nocera Umbra (central Italy) 总被引：2，自引：1，他引：1
F. Marra R. Azzara F. Bellucci A. Caserta G. Cultrera G. Mele B. Palombo A. Rovelli E. Boschi 《Journal of Seismology》2000,4(4):543-554
During the two mainshocks of September 26, 1997 inthe Umbria-Marche border a strong-motion accelerographrecorded peak ground accelerations as large as 0.6 g,approximately, in the town of Nocera Umbra, atdistances of 10 to 15 km from the epicentres. Thisvalue is significantly larger than expected on thebasis of the usual regressions with magnitude anddistance. A broad-band amplification up to a factor of10 was consistently estimated in previous papers,using both weak and strong motion data recorded at theaccelerograph site during local moderate earthquakes.To study the cause of this amplification we deployedsix seismologic stations across the tectonic contactbetween the Ceno-Mesozoic limestone and the Mesozoicmarly sandstone where the accelerograph is installed.Seismograms of 21 shallow aftershocks in the magnituderange from 2.2 to 4.0 and a subcrustal Mw = 5.3event are analysed. Regardless of epicentre location,waveforms show a large complexity in an approximately200 m wide band adjacent to the tectonic contact. Thisis interpreted as the effect of trapped waves in thehighly fractured, lower velocity materials within thefault zone. 相似文献
10.
A. Caserta S. Martino F. Bozzano A. Govoni F. Marra 《Bulletin of Earthquake Engineering》2012,10(4):1133-1162
The presence of peats and high compressibility inorganic clays within alluvial fills on the left-side tributaries of the Tiber River, close to Rome’s historic center in Italy, is well documented in literature. Nevertheless, few literature data exist until now on the dynamic properties of these deposits by undisturbed bore-hole samples. The Galba test-site was set up to characterise dynamic properties of the alluvial deposits by using lab-tests as well as to derive velocity profiles by seismic noise measurements. These were performed in the Giustiniano Imperatore area located in the Grottaperfetta valley, about 2?km south of Rome’s historic centre. The alluvial deposits filled a paleovalley excavated in the bedrock during the Würm glacial (18–20 ky). The stratigraphic setting of the alluvial body was reconstructed along three geological cross-sections by means of the available logs; seven lithotecnical horizons can be distinguished within the alluvial body, some tens of meters thick, based on both log-stratigraphic data and in-site geotechnical tests. These horizons include peaty layers (T) and high compressibility inorganic clays (AGI), which characterise the alluvial deposits in the Grottaperfetta valley. They do not have direct correlation with the alluvial horizons which constitute the alluvial body of the main Tiber valley in Rome’s historical centre. These alluvial horizons which are distinguished and characterised at the Galba test-site can be regarded as typical of other lateral valleys of the Tiber River in Southern Rome. They are characterised by the presence of similar high compressibility clayey deposits as well as peaty layers up to some meters thick. Undisturbed samples were also obtained at the Galba test-site for dynamic testing via resonant column and cyclic torsional shear tests. In order to attribute dynamic properties to the alluvial body at the Grottaperfetta valley, an extrapolation process was performed based on a detailed engineering-geology model of the alluvial body which was reconstructed along three transversal geological sections of the valley using bore-hole data. Three subsoil profiles, considered representative of the geological setting along the three reconstructed transversal cross sections, were analysed by seismic noise measurements performed specifically to derive S-waves velocity profiles. The results obtained show a very low velocity (<180 m/s) for the layers T and AGI. 1D modelling of seismic shaking was performed by the code Shake91, in order to evaluate the influence of the low-velocity strata on maximum shear strains induced within the alluvial deposits under the maximum expected seismic action. The results of the numerical modelling indicate that the AGI and the T layers play a key role in: (i) concentrating the maximum shear strain along the subsoil profiles, even though the volumetric threshold is never exceeded; (ii) increasing the maximum shear strain along the subsoil profiles; (iii) causing the resonance frequency of the alluvial fill to assume an almost constant value (about 1Hz) which is quite similar to that measured in the main Tiber River valley, despite a significant change in thickness of the alluvial body along the Grottaperfetta valley. 相似文献