stable carbon and oxygen isotopic evidence for late pleistocene to middle holocene climatic fluctuations in the interior of southern africa stable carbon and oxygen isotope analyses of ungulate grazers from four archaeolog ical sites located in different environs within the caledon river valley have provided a relatively well dated proxy palaeoenvironmental and palaeoclimatic sequence for the period between 16 000 and 6000 calendar cal yr bp within the overall trend towards hot mid holocene temperatures and a summer rainfall pattern stable carbon isotope results show that there were three periods when growth season temperatures were cool enough for c3 grasses to be present 16 000 14 000 10 200 9600 and 8400 8000 cal yr bp similar trends were recorded in stable oxygen isotope values reflecting shifts in either temperature or available moisture although having a similar pattern to that of the lower altitude site sites situated in foothills and montane portions of the valley consistently maintained lower temperatures until the mid holocene altithermal at this time growth season temperatures warmed sufficiently for a 100 c4 grassland to expand in altitude from the warmer low lying localities in relation to present understanding of synoptic and global climatic patterning these findings suggest that the early to middle holocene transition was not a gradual warming trend but rather it was marked by a series of climatic fluctuations of particular note is the possible global rather than regional occurrence of the 8200 cal yr bp event copyright 2002 john wiley sons ltd journal of quaternary science

persistent millennial scale climatic variability over the past 25 000 years in southern africa abstract data from stalagmites in the makapansgat valley south africa document regional climatic change in southern africa in the late pleistocene and holocene a new tims u series dated stalagmite indicates speleothem growth from 24 4 to 12 7 ka and from 10 2 to 0 ka interrupted by a 2 5 ka hiatus high resolution oxygen and carbon stable isotope data suggest that postglacial warming was first initiated 17 ka was interrupted by cooling probably associated with the antarctic cold reversal and was followed by strong warming after 13 5 ka the early holocene experienced warm evaporative conditions with fewer c4 grasses cooling is evident from 6 to 2 5 ka followed by warming between 1 5 and 2 5 ka and briefly at ad 1200 maximum holocene cooling occurred at ad 1700 the new stalagmite largely confirms results from shorter holocene stalagmites reported earlier the strongest variability superimposed on more general trends has a quasi periodicity between 2 5 and 4 0 ka also present are weaker 1 0 ka and 100 year oscillations the latter probably solar induced given similarities to the antarctic records the proximate driving force producing millennial and centennial scale changes in the makapansgat record is postulated to be atmospheric circulation changes associated with change in the southern hemisphere circumpolar westerly wind vortex

late quaternary vegetation dynamics and hydro climate in the drakensberg south africa abstract a multi proxy study of a sediment sequence from braamhoek wetland covering the last c 16 000 years reveals a record of regional climate and vegetation dynamics in the drakensberg region south africa including signals from both the organic sediment fraction fossil pollen charcoal n alkane abundance n alkane 13c toc and the inorganic fraction mineral magnetic properties the reconstruction supported by a robust chronology indicates two major periods of increased regional wetness during the late pleistocene to early holocene phase c 13 800 12 600 cal yr bp c 10 200 8500 cal yr bp and one during the late holocene c 2000 cal yr bp to present drier conditions are recorded during the younger dryas c 12 600 11 300 cal yr bp and mid holocene c 7000 2000 cal yr bp a major decline in fynbos vegetation during the early holocene suggests a shift towards warmer temperatures and possibly towards less pronounced winter rains in eastern south africa from c 8500 cal yr bp comparison with records from interior of south africa show relatively high inter site variability however the braamhoek moisture proxies do co vary with the speleothem isotope records from makapansgat suggesting a similar hydro climate evolution in eastern and interior parts of the summer rainfall region during the studied period on multi millennial time scales an inverse hydro climatological pattern is evident between these two south african records and reconstructions from tropical locations in southeast africa such a rainfall dipole between eastern tropical and southern africa has previously been identified on shorter time scales i e on inter annual to millennial scales the braamhoek study suggests that a similar dipole pattern is acting also on a multi millennial perspective these long term precipitation anomalies are tentatively coupled to teleconnections from multi millennial changes in the dynamics of the indian ocean dipole iod and el nino southern oscillation enso

the validity of the asteraceae poaceae fossil pollen ratio in discrimination of the southern african summer and winter rainfall zones abstract situated at the transition between the mid latitudes and the sub tropics southern africa has a climatic dichotomy between winter and summer rainfall zones wrz and srz the latitudinal extent of the winter rainfall zone during the late pleistocene remains contentiously debated within the regional palaeoscience literature one method posited to reflect the seasonality of rainfall at a given location throughout late pleistocene records for south africa is the ratio of fossil pollen asteraceae to poaceae although adopted for a range of southern african locations the veracity of this method has not been tested this study explores the extent to which this ratio can discriminate between the srz and wrz and the extent of the region subject to fluctuation during the late quaternary the ratio is found to successfully discriminate regions which are and would have remained during the past 20 000 cal yr bp in the srz and wrz exclusively on the basis of these statistics it appears that wrz conditions can be inferred from ratio scores 0 6 and srz conditions from scores

theory and calibration of the pierre 2 stochastic rock fall dynamics simulation program the use of computer models to determine rock fall hazards is increasingly common with increasingly complex models being developed in most practical applications slopes potentially affected by ro

slip history and dynamic implications of the 1999 chi chi taiwan earthquake we investigate the rupture process of the 1999 chi chi taiwan earthquake using extensive near source observations including three component velocity waveforms at 36 strong motion stations and 119 gps measurements a three plane fault geometry derived from our previous inversion using only static data ji et al 2001 is applied the slip amplitude rake angle rupture initiation time and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm ji et al 2002b the inversion results are validated by the forward prediction of an independent data set the teleseismic p and sh ground velocities with notable agreement the results show that the total seismic moment release of this earthquake is 2 7 10 20 n m and that most of the slip occurred in a triangular shaped asperity involving two fault segments which is consistent with our previous static inversion the rupture front propagates with an average rupture velocity of 2 0 km s 1 and the average slip duration risetime is 7 2 s several interesting observations related to the temporal evolution of the chi chi earthquake are also investigated including 1 the strong effect of the sinuous fault plane of the chelungpu fault on spatial and temporal variations in slip history 2 the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation and 3 the observation that the peak slip velocity near the surface is in general higher than on the deeper portion of the fault plane as predicted by dynamic modeling

finite fault inversion of dinsar coseismic displacement of the 2009 l aquila earthquake central italy 1 we define the geometric and kinematic characteristics of the fault activated during the mw 6 3 6 april 2009 l aquila earthquake from the modeling of envisat and cosmo skymed the first ever x band interferogram inverted for a coseismic dislocation study dinsar interferograms our best fit solution for the main shock is represented by a normal fault 16 km long and 12 km wide with a small right lateral component dipping 47 sw with a maximum slip of 90 cm although the seismic dislocation probably ended at 1 km depth the updip projection of the fault plane corresponds to the northern segment of the mapped paganica s demetrio fault where alignment of surface breaks was observed in the field the absence of this fault in existing seismic source catalogues suggests that an improved approach involving detailed surface and subsurface geological and geophysical investigations is needed for a better assessment of the seismic hazard at the local scale

holocene climate variability and change a data based review the holocene thermal maximum with peak temperatures prior to 7 ka bp is mostly accentuated in the northern hemisphere still visible in the southern hemisphere and possibly did not exist in the tropics between this period and the modern warming a remarkable negative temperature trend occurred in the northern hemisphere which was probably the effect of a decreasing orbital induced insolation during the boreal summer on average the northern hemisphere humidity precipitation records do not show any significant trend a mechanistic explanation for the multi decadal to century scale holocene cold relapses which mainly occurred in the atlantic european regions exists for only the early holocene cooling events which are probably the result of a collapse of the meridional overturning circulation owing to freshwater outbursts from the laurentide ice sheet possibly the late holocene cold events after c 4 ka bp are influenced by the covarying influence of major tropical volcanic eruptions and grand solar minima

effect of impact velocity block mass and hardness on the coefficients of restitution for rockfall analysis abstract one of the most significant input parameters in rockfall trajectory modelling is the coefficient of restitution which controls block rebound in particular in the design of rockfall barriers it can significantly affect their height in practice the coefficients of restitution are acquired by field or laboratory tests back analyses of known events experience or most commonly suggested values connected to the slope material furthermore to account for the effect of impact velocity or block mass scaling factors are available however the suggested values are based on a qualitative description of the slope material and the scaling factors are not well documented nor do they account for the effects of impact velocity and block mass simultaneously in this paper a semi empirical correlation is proposed that takes into account the schmidt hammer rebound value of both the slope and block material as well as the impact velocity and block mass this was derived by an extensive laboratory experimental study 445 impact tests of a one dimensional drop of spherical blocks onto planar surfaces the semi empirical correlation proposed adequately describes the responses observed under the circumstances imposed in the laboratory

climate change during the last deglaciation in antarctica greenland ice core records provide clear evidence of rapid changes in climate in a variety of climate indicators in this work rapid climate change events in the northern and southern hemispheres are compared on the basis of an examination of changes in atmospheric circulation developed from two ice cores high resolution glaciochemical series covering the period 10 000 to 16 000 years ago from a central greenland ice core and a new site in east antarctica display similar variability these findings suggest that rapid climate change events occur more frequently in antarctica than previously demonstrated

structural and thermal controls of rockfall frequency and magnitude within rockwall talus systems swiss alps both from a systemic and natural hazard perspective it is essential to understand the causes and frequency of rockfalls in mountain terrain and to predict the block sizes deposited at specific locations commonly rockfalls are studied either retrospectively using talus slopes or directly by rockwall surveys nevertheless our understanding of rockfall activity particularly at the lower magnitude spectrum is still incomplete moreover the explanatory framework is rarely addressed explicitly in this study we investigate two rockwall talus systems in the swiss alps to estimate the rockfall frequency magnitude pattern and their key controls we present a holistic approach that integrates deductive geotechnical and thermal investigations of the source rockwalls with abductive talus based explanations of rockfall volume and frequency the rockwalls three dimensional 3d joint pattern indicates that 75 of the blocks may be released as debris fall 14 m3 and boulder falls 14 61 m3 which is mirrored in the corresponding talus material using two year records of near surface rockwall temperatures as input for a 1d heat conduction model underlines the destabilizing role of seasonal ice segregation deepest frost cracking of 300 cm may occur on the north northeast nne exposed snow rich rockwall with peaks at the outermost surface the synthesis of all data suggests that infrequent large planar slides approximately every 250 years overlain by smaller more frequent wedge and toppling failures approximately every 17 50 years as well as high frequency flake like clasts 3 6 events year characterize the rockfall frequency magnitude pattern at hungerli peak here we argue that small size rockfalls need more scientific attention particularly in discontinuous permafrost zones our study emphasizes that future frequency magnitude research should ideally incorporate site specific structural and thermal properties rather than just focusing on climatic or meteorological triggers we discuss how holistic rockwall talus approaches as proposed here could help to increase our process understanding of rockfalls in mountain environments copyright 2017 john wiley sons ltd

rockfall analysis along transportation corridors in high hill slopes the paper discusses the problems pertinent to rockfall activities in highly jointed rock cut slopes excavated without detailed geotechnical and geological investigations along the right bank of river sutlej luhri himachal pradesh india the cut slopes are near vertical to sub vertical and overhangs are ubiquitous at several locations initially probable zones of slope failure were identified from field inspection and kinematic analysis the study then uses 2d rockfall analysis for estimating loss of energy due to the impact of falling blocks on the slope face and subsequently on the road several parameters were also assessed from the study viz bounce height travel distance kinetic energy and translational velocity the result from rockfall analysis shows that the energy and velocity achieved by the falling blocks are considerably high capable enough to cause severe damage in relation to energy and velocity bounce height achieved is not very large because of removal of trees from the slopes face and no measures to capture falling blocks the problems have been aggravated and therefore most of the rock covers very large distance to reach up to the valley crossing the roadways endangering travelers and infrastructures based on the results preventive measures have been suggested to prevent future rockfall hazards

integrating high precision aftershock locations and geodetic observations to model coseismic deformation associated with the 1995 kozani grevena earthquake greece 1 we integrate high precision aftershock locations with geodetic inverse modeling to create a more complete kinematic model for the kozani grevena earthquake sequence using the double difference algorithm we have improved relative hypocentral locations by a factor of 7 and thus imaged the details of the fault network associated with the seismic sequence the interpreted fault network consists of multiple segments including 1 a master normal fault that strikes nearly due west and dips toward the north at 43 extending from 6 to 15 km depth 2 an upper segment that connects the top of the seismicity to the observed surface ruptures and dips 70 3 hanging wall antithetic faults 4 a more steeply dipping southwest striking linking structure at the southwest end of the rupture and 5 a separate south dipping segment at the southwestern end of the aftershock cluster the imaged fault segment dimensions orientations and geometric relationships are consistent with regional fault patterns using slip inversion on triangular dislocation patches we calculate variable slip on the imaged three dimensional fault network that best fits the surface displacements observed by satellite interferometric synthetic aperture radar insar in our preferred model we find that the majority of slip occurred at depth on the west and southwest striking segments by comparing these results to a planar fault model derived solely from the insar data using nonlinear inversion methods we demonstrate that the three dimensional model improves the fit to the geodetic data while incorporating the observations of surface rupturing and aftershock distributions

poleward decrease in the isotope effect of nitrate assimilation across the southern ocean recent studies provide seasonally and spatially resolved information on the isotopic characteristics of nitrate supply and n cycling in southern ocean surface waters the new data improve our understanding of the nitrate supply to the antarctic surface and its isotopic characteristics especially with regard to the summertime subsurface minimum temperature t min layer in the antarctic we use these findings to update and compile estimates of the n isotope effect of nitrate assimilation e in the southern ocean near australia a poleward decrease in e emerges from 8 9 in the subantarctic zone saz 40 52 s to similar to 5 in the polar antarctic zone paz 66 s e is strongly correlated with mixed layer depth at the time of sampling we hypothesize that the correlation is driven by the physiological response of diatoms to light availability with light limitation leading to higher cellular efflux of nitrate and thus higher e

coseismic deformation of the destructive april 6 2009 l aquila earthquake central italy from gps data 1 on april 6 2009 01 32 39 gmt the city of l aquila was struck by a mw 6 3 earthquake that killed 307 people causing severe destruction and ground cracks in a wide area around the epicenter four days before the main shock we augmented the existing permanent gps network with five gps stations of the central apennine geodetic network cageonet bordering the l aquila basin the maximum horizontal and vertical coseismic surface displacements detected at these stations was 10 39 0 45 cm and 15 64 1 55 cm respectively fixing the strike direction according to focal mechanism estimates we estimated the source geometry with a non linear inversion of the geodetic data our best fitting fault model is a 13 15 7 km2 rectangular fault sw dipping at 55 3 1 8 consistent with the position of observed surface ruptures the estimated slip 495 29 mm corresponds to a 6 3 moment magnitude in excellent agreement with seismological data

shifting westerlies and precipitation patterns during the late pleistocene in southern africa determined using glacier reconstruction and mass balance modelling abstract south africa experiences a range of different climatic regimes and is thus an ideal region to investigate late pleistocene environmental and climate change however detailed quantifiable palaeoclimate data are sparse in the region in particular reliable palaeoclimatic data are essential to resolve ongoing controversies regarding temperature depression and moisture availability during glacial periods in the sub continent small glaciers close to the glaciation threshold are highly sensitive to changes in temperature and precipitation and are therefore ideal indicators of past climatic conditions during their existence this paper derives some of the first quantitative data on last glacial maximum lgm palaeoprecipitation in southern africa based on glacier reconstruction and mass balance modelling for the lesotho highlands the reconstruction of former glaciers and their dynamics enables the determination of glacier viability under specific climatic envelopes glacier reconstructions at five sites in the lesotho highlands yield palaeoglaciers with equilibrium line altitudes elas ranging from 3095 to 3298 m a s l and reconstructed steady state mass balance and flow dynamics are comparable with modern analogues topoclimatic factors are investigated with temperature radiation index modelling indicating that topographic shading was an important factor determining the existence of small glaciers in this region the occurrence of glaciation in the drakensberg during the lgm suggests a potential increase in precipitation and change in its seasonality such trends are likely associated with an increased frequency of westerly wave cold front disturbances due to the northward shift of pressure belts which would also increase precipitation as snow at higher altitudes the application of a high resolution climate model hadam3h to test this displays a change in the seasonal timing of precipitation during the last glacial cycle with a decrease in precipitation evident during the summer months this is likely to have had important implications for the mass balance and survival of small niche glaciers in the region with more precipitation falling during the spring winter autumn months as snow

siliceous microfossils as late quaternary paleo environmental indicators at braamhoek wetland south africa this thesis contributes with information on past climate and environmental changes in south africa s summer rainfall region the study is based on multi proxy analyses on wetland peat cores and analyses of stable isotope composition 13c 18o and wood anatomy in cross sections from subtropical trees breonadia salicina the peat archive covers the last 16 ka ka 1000 cal yrs bp and was analysed in terms of fossil pollen charcoal diatoms phytoliths and stable isotope composition the peat record infers relatively wet climate conditions at c 13 7 12 8 ka 10 5 9 5 ka and 2 5 0 5 ka and drier conditions at c 16 13 7 ka 12 8 10 5 ka and during mid holocene tentatively cooler late pleistocene temperatures shifted towards warmer after c 9 5 ka the study of b salicina demonstrates the paleo climatic value of subtropical trees despite absence of annual tree rings an age model was constructed from radiocarbon dating and calibration by wiggle matching 13c in b salicina shows a co variation with annual rainfall amounts suggesting that it may be considered a regional climate proxy 18o is mainly influenced by local factors but acts as a useful complement when interpreting 13c together with other regional high resolution records the 600 year long 13c record suggests dry climate conditions in northern south africa during the 1700s and mid 1500s ad inferred climate and environmental changes are suggested being a response to expansion contraction and latitudinal shifts of the tropical subtropical and mid latitude atmospheric circulation cells an observed inverse humidity pattern between southern and equatorial africa suggests that enso like teleconnections may be a possible forcing mechanism in a decadal to centennial time perspective

experimental study on the river blockage and landslide dam formation induced by rock slides abstract rock slides triggered by strong earthquake or heavy rainfall may cause different degrees of blockage in flow channels resulting in a significant impact on the continuity of mountainous rivers based on the extent of blocking the blockage type is divided into three categories in this paper no blockage submerged dam partial blockage and complete blockage the accumulation process of sliding materials in the course of rock slides is an important issue for understanding the formation of landslide dams in this study rock slide and river valley models are developed to investigate the typical kinematic process and emplacement of rock slides and the factors that dictate the formation of landslide dams are critically analyzed the experimental study suggests that there is a positive correlation between the deposit height and the rock slide volume despite differences of rock fragmentation and flow condition in addition the less fragmented rocks result in larger maximum deposit height maxi dh and smaller minimum deposit height mini dh while the better fragmented rocks result in smaller maxi dh and larger mini dh furthermore the water depth has a significant impact on the river blockage type a new blockage index bi that combines the landslide volume and the wet cross sectional area is proposed to assess the damming capacity of rock slides then a method for predicting the river blockage type of rock slides is developed based on the relationship between blockage index and the ratio of maxi dh or mini dh and water depth the model proposed in this work can be used to assist estimating the formation of landslide dam for similar rock slides in the future

direct observation of rupture propagation during the 1979 imperial valley earthquake using a short baseline accelerometer array abstract the 1979 imperial valley california earthquake m s 6 9 was recorded on the el centro differential array a 213 m long linear array of 5 three component digital accelerometers 5 6 km from the nearest tectonic surface rupture although absolute time was not recorded on the array elements a relative time base was established using the main shock hypocentral p wave and the p and s waves from a later aftershock a cross correlation technique was used to measure the difference in arrival times of individual seismic waves in a moving 0 6 to 1 2 sec window at each array element which would then be converted into the wave9s slowness 1 velocity along the array when applied to the main shock vertical and horizontal accelerograms results from both components of motion indicated that the early arriving energy came from a source to the south of the array and the source of the energy moved rapidly to the north of the array during the strong shaking the ground motions at the array elements were well correlated for about the first 11 sec of motion these observations suggest that we have observed the initiation of rupture south of the array and its subsequent propagation along the fault to a position north of the array in about 10 sec and that the energy was radiated from a fairly compact region around the rupture front if the observed vertical and horizontal ground motions are assumed to be caused by p and s waves respectively then the observed slownesses show irregularities which can be interpreted as implying that the observed high frequency ground motions originated at irregularly distributed regions on the fault surface or that the rupture velocity was variable or both one possible interpretation of the data suggests that the rupture proceeded at near p wave velocity over a 7 km long section of fault average rupture velocities of about 2 7 to 3 2 km sec at 8 km depth are consistent with the data and 2 8 km sec is weakly preferred under the assumption that rupture propagates at a fixed fraction of the shear velocity the large vertical pulse which had a peak acceleration of 1 7 g at e06 was emitted from the portion of the fault extending 25 to 30 km northwest of the hypocenter near meloland overpass and not from the point on the fault closest to the differential array nothing can be said about fault behavior southeast of the hypocenter

a multi proxy analysis of late quaternary palaeoenvironments sekhokong range eastern lesotho the eastern lesotho highlands host an array of periglacial and glacial geomorphic features their analysis has provided past climate interpretations predominantly for cold periods yet no multi proxy temporally continuous palaeoenvironmental records exist this study presents a palaeoenvironmental reconstruction based on sedimentary characteristics fossil pollen and diatoms from an alpine wetland located in the sekhokong mountain range the record commences in the late pleistocene with a wet period from 16 450 to 14 440 cal a bp interrupted by dry conditions from 16 350 to 15 870 cal a bp from 14 150 to 8560 cal a bp drier conditions are inferred slowly transitioning to warmer wetter conditions warmer dry conditions are inferred for 8560 7430 cal a bp followed by cold wet conditions from 7280 to 6560 cal a bp a dry warmer period occurs from 6560 to 3640 cal a bp indicated by pollen diatom and sedimentary records followed by cool wet conditions from 3400 to 1200 cal a bp the period from 1110 cal a bp to the present is characterized by progressive drying pronounced cold events are detected from the diatom record moisture records appear relatively specific to the topographic setting of sekhokong near the great escarpment edge probably driven by orographically constrained synoptic controls

aquatic ecosystem responses to holocene climate change and biome development in boreal central asia boreal ecosystems are highly vulnerable to climate change and severe ecological impacts in the near future are virtually certain to occur we undertook a multiproxy study on an alpine lake esm 1 at the modern tree line in boreal southern siberia steppe and tundra biomes were extensive in eastern sayan landscapes during the early holocene boreal forest quickly expanded by 9 1 ka bp and dominated the landscape until c 0 7 ka bp when the greatest period of compositional turnover occurred at this time alpine meadow landscape expanded and picea obovata colonised new habitats along river valleys and lake shorelines because of prevailing cool moist conditions during the early holocene chironomid assemblages were dominated by cold stenotherms diatoms for much of the holocene were dominated by alkaliphilous fragilarioid taxa up until 0 2 ka bp when epiphytic species expanded indicative of increased habitat availability c n mass ratios ranged between 9 5 and 13 5 11 1 15 8 c n atomic ratios indicative of algal communities dominating organic matter contributions to bottom sediments with small persistent contributions from vascular plants however 13c values increased steadily from 34 9 during the early holocene 9 3 ka bp to 24 8 by 0 6 ka bp this large shift in magnitude may be due to a number of factors including increasing within lake productivity increasing disequilibrium between the isotopic balance of the lake with the atmosphere as the lake became isotopically mature and declining soil respiration linked to small but distinct retreat in forest biomes the influence of climatic variables on landscape vegetation was assessed using redundancy analysis rda a linear direct ordination technique changes in july insolation at 60 n significantly explained over one fifth of the variation in species composition while changes in estimates of northern hemisphere temperature and ice rafted debris events in the north atlantic were also significant but considerably less important the potential importance of climate and biome development tundra steppe cold deciduous forest and taiga on different trophic levels i e chironomid and diatom communities in lake esm 1 was also assessed using rda climate predictors had a more significant influence on holocene chironomid assemblages especially july insolation at 60 n estimates of regional precipitation and estimates of northern hemisphere temperature while only the development of the taiga biome had a significant impact on these primary consumers diatom communities also had a small but significant influence on holocene chironomid populations perhaps linked to variation in faunal feeding strategies in contrast climatic and biome predictors explained similar amounts of variation in the holocene diatom assemblage approximately 20 each while chironomids themselves as predictors explained just under 7 of diatom variation lake acidity was inferred using a diatom inference model results suggest that after deglaciation the lake did not undergo a process of gradual acidification most likely due to the presence of continuous permafrost and low levels of precipitation preventing base cations and dissolved organic carbon entering the lake except for the period between 1 7 and 0 7 ka bp we conclude that lakes in continental boreal regions undergo different models of lake ontogeny than oceanic boreal regions unlike other regions discussed climate is a more important driver of ecosystem change than catchment changes we also demonstrate that the start of the period coincident with the onset of the little ice age resulted in important thresholds crossed in catchment vegetation and aquatic communities

modeling rockfall frequency and bounce height from three dimensional simulation process models and growth disturbances in submontane broadleaved trees the use of dynamic computational methods has become indispensable for the assessment of rockfall hazards and the quantification of uncertainties although a substantial number of models with various degrees of complexity has become available over the past few years models have only rarely been parameterized against observations especially because long term records of rockfalls have proven to be scarce and typically incomplete on forested slopes tree ring analyses may help to fill this gap as they have been shown to provide annually resolved data on past rockfall activity over long periods in this paper a total of 1495 rockfall scars recorded on the stem surface of 1004 trees have been studied at a site in the vercors massif french alps to calibrate the 3d process based simulation model rockyfor3d uncertainties related to the choice of parameters accounting for energy dissipation and surface roughness have been investigated in detail because of the lack of reliable data these parameters typically are estimated based on expert judgments despite the fact that they have significant impacts on runout distances and bounce height we demonstrate that slight variations in roughness can indeed strongly affect the performance of runout modeling and that the decreasing downward gradient observed in field data is properly reproduced only if reduced roughness 10 cm enables blocks to reach the distal parts of the study plot with respect to the height of impacts our results also reveal that differences between simulations and observations can indeed be minimized if softer soil types are preferred during simulation as they typically limit bouncing we conclude that field based dendrogeomorphic approaches represent an objective tool to improve rockfall simulations and to enhance our understanding of parameterization which is of key importance for process dynamics and thus hazard zoning

why large earthquakes do not nucleate at shallow depths although by definition tectonic earthquakes may nucleate anywhere within the seismogenic layer in almost all cases those earthquakes that become large nucleate near the base of the seismogenic layer because frictional strength and stress drop should increase with depth and in situ stress measurements suggest that the ambient stress increases with depth we have examined spontaneous rupture models with gradients of both average stress drop and average strength relative to ambient stress to determine whether this explains the observed phenomena we report here that ruptures that are nucleated with in the low stress drop shallow regions of the model are inhibited from propagating but those that are nucleated within the high stress drop regions can propagate over the entire fault plane

late quaternary dynamics of southern africa s winter rainfall zone abstract variations in the nature and extent of southern africa s winter rainfall zone wrz have the potential to provide important information concerning the nature of long term climate change at both regional and hemispheric scales positioned at the interface between tropical and temperate systems southern africa s climate is influenced by shifts in the intertropical convergence zone the westerlies and the development and position of continental and oceanic anticyclones over the last glacial interglacial cycle substantial changes in the amount and seasonality of precipitation across the subcontinent have been linked to the relative dominance of these systems central to this discussion has been the extent to which the region s glacial climates would have been affected by expansions of antarctic sea ice equatorward migrations of the westerlies more frequent intense winter storms and an expanded wrz this paper reviews the developing body of evidence pertaining to shifts in the wrz and the evolution of ideas that have been presented to explain the patterns observed dividing the region into three separate axes along the western and southern margins of the continent and across the interior into the karoo and the kalahari a range of evidence from both terrestrial sites and marine cores is considered and potential expansions of the wrz expansions are explored despite the limitations of many of the region s proxy records a coherent pattern has begun to develop of a significantly expanded wrz during phases of the last glacial period with the best documented being between 32 17 ka while more detailed inferences will require the recovery and analysis of longer and better dated records this synthesis provides a new baseline for further research in this key region

pollen indications of holocene palaeoenvironments at florisbad spring in the central free state south africa mid to late holocene pollen data from florisbad in the central free state south africa reveal a number of moisture fluctuations commencing at c 6500 bp the pollen sequence indicates an arid climate but shows more availability of moisture under grassy conditions from summer rain at c 6300 bp and again at c 4420 bp the interval between these dates is characterized by a dry episode with karroid shrubs some time between 5500 and 4500 bp possibly as a result of less marked summer seasonality after 4220 bp moisture conditions gradually fluctuated in intensity or seasonal availability until c 2100 1700 bp when strong summer evaporation is indicated at the upper end of the sequence the data are complemented by previously published results on environmental change from the nearby deelpan site to the west although some distinct events correlate regionally over south africa summer rains appear to have been significant at florisbad at an earlier stage in the mid holocene than in the karoo to the south

late quaternary peat accumulation in southern africa abstract it is suggested that the accumulation of peat deposits and other organic sediment may be a clue to the timing of moister periods in the late quaternary climatic history of southern africa data presented from 26 sites across the sub continent point to two periods during which organic sedimentation commenced suggesting a moister late pleistocene and a period during the mid late holocene when conditions also became more conducive to peat formation owing to the confusing and conflicting nature of other palaeoenvironmental information organic sediment accumulation chronologies seem to provide additional insight into the environmental history of southern africa and the implications of this are discussed

geometry of continental normal faults seismological constraints teleseismic body waves from large earthquakes are used to study the downdip geometry of continental normal faults in the aegean waveform modeling techniques together with rigorous statistical tests are applied to put firm bounds on the amount of downdip curvature of these faults and the role of coseismic slip on a basal detachment synthetic modeling shows that good azimuthal station coverage and inclusion of sh waves are necessary to resolve fault curvature the data indicate ruptures of the aegean events occurred on planar faults extending across the entire brittle portion of the crust no seismogenic low angle detachment faulting at the base of the upper crust was detected for these events decoupling of the brittle upper crust from the plastic lower crust probably occurs aseismically in a ductile fashion

low angle normal fault earthquakes and triggering geologic evidence for low angle normal faulting is overwhelming and recent seismic geodetic and neotectonic studies have identified probable active examples thus apparent low levels of historical seismicity on such faults is enigmatic however one large mainshock was a low angle normal event and three others may have been one earthquake sequence had significant moment release from a triggered low angle normal fault and three earthquakes may have had normal subevents on low angle planes such sub events are hard to recognize may be underrepresented in catalogs helping to explain the apparent seismic enigma and pose increased seismic hazard due to delayed strong motions triggered sub events may be along strike or down dip from their triggering shock in cases where the triggered slip is downdip of the steep fault and under its hanging wall elevated pore fluid pressure or fault weakness may be required

the anatomy of the 2009 l aquila normal fault system central italy imaged by high resolution foreshock and aftershock locations 1 on 6 april 01 32 utc 2009 a mw 6 1 normal faulting earthquake struck the axial area of the abruzzo region in central italy we study the geometry of fault segments using high resolution foreshock and aftershock locations two main sw dipping segments the l aquila and campotosto faults forming an en echelon system 40 km long nw trending the 16 km long l aquila fault shows a planar geometry with constant dip 48 through the entire upper crust down to 10 km depth the campotosto fault activated by three events with 5 0 mw 5 2 shows a striking listric geometry composed by planar segments with different dips along depth rather than a smoothly curving single fault surface the investigation of the spatiotemporal evolution of foreshock activity within the crustal volume where the subsequent l aquila main shock nucleated allows us to image the progressive activation of the main fault plane from the beginning of 2009 the foreshocks activated the deepest portion of the fault until a week before the main shock when the largest foreshock mw 4 0 triggered a minor antithetic segment seismicity jumped back to the main plane a few hours before the main shock secondary synthetic and antithetic fault segments are present both on the hanging and footwall of the system the stress tensor obtained by inverting focal mechanisms of the largest events reveals a ne trending extension and the majority of the aftershocks are kinematically consistent deviations from the dominant extensional strain pattern are observed for those earthquakes activating minor structures

earthquake source mechanisms from body waveform inversion and intraplate tectonics in the northern indian ocean double couple point source parameters for 11 of the largest intraplate earthquakes in the northern indian ocean during the last 20 y were determined from a formal inversion of long period p and sh waveforms nine of the events have centroid depths at least 17 km below the seafloor well into the upper mantle two have centroid depths as great as 39 km using the source mechanisms of these earthquakes we distinguish two major intraplate tectonic provinces in the northern indian ocean to the west of the ninetyeast ridge in the southern bay of bengal intraplate earthquakes have thrust faulting mechanisms with p axes oriented n s the centroid depths of these earthquakes range from 27 to 39 km below the seafloor lithospheric shortening in this region is thus accomplished by thrust faulting in the strong core of the oceanic upper mantle while other geophysical evidence suggests that shallow sedimentary and crustal layers apparently deform predominantly by folding in the immediate vicinity of the ninetyeast ridge earthquakes display strike slip mechanisms with left lateral motion on planes parallel to the ridge this type of faulting occurs from at least 10 s to the northern end of the ninetyeast ridge near 10 n where the ridge meets the sunda arc seismic activity diminishes to the east of the ninetyeast ridge but is also characterized by strike slip faulting despite these variations in deformational style the inferred orientation of greatest compressive stress in the northern indian ocean displays a consistent long wavelength pattern over a large portion of the indian plate varying smoothly from nearly n s in the bay of bengal to nw se in the northeastern indian ocean this plate wide stress pattern and the high level of intraplate seismicity in the northern indian ocean are likely the results of substantial resistance along the himalayan continental collision zone to the continued northward motion of the western portion of the indian plate oceanic intraplate earthquakes in other regions where the level of deviatoric stress associated with the long wavelength part of the stress field is likely to be smaller need not be comparably reliable indicators of the plate wide stress field

geodetic investigation of the 13 may 1995 kozani grevena greece earthquake the ms 6 6 13 may 1995 kozani grevena earthquake struck a region of low historical seismic activity which includes a 10 year old triangulation network in northern greece after the earthquake monuments from this network were occupied with gps to measure co seismic displacements inversion of the co seismic displacement field to yield a source mechanism is achieved by use of a hybrid simplex monte carlo method which requires no a priori constraints the model focal mechanism agrees well with the global cmt solution and locally observed aftershocks but implies a significantly higher scalar moment than do seismological or sar interferometry studies and has a longer fault length than the model based on sar interferometry

drainage network morphometry and evolution in the eastern lesotho highlands southern africa abstract present day drainage patterns in mountain regions are strongly affected by antecedent tectonic and geologic factors in the mountains of eastern lesotho southern africa bedrock comprises flat lying jurassic basalts which have given rise to a relatively uniform initial land surface here we present key morphometric measurements of river drainage patterns from this region from six 4th order river basins including principal river sinuosity river long profiles and valley cross profiles in order to evaluate geological controls on drainage evolution and the potential ages of river elements results show that there are highly variable spatial patterns of river morphometric properties even between adjacent basins despite identical geologies and altitudes across the region however northerly catchments show knickpoints variable long profiles and have steep sided and v shaped valley cross profiles southerly catchments have much smoother long profiles no knickpoints and concavo convex valley cross profiles there are also differences in river sinuosity values both for the catchments as a whole and for reaches of different lengths within the catchments these spatially varying river morphometric and drainage properties most likely are the long preserved outcomes of epeirogenic forcing on the land surface including tectonic uplift mantle relaxation and rebound during the cenozoic and subtle long term variations in climate from north to south across the region including in precipitation and weathering

alpine turf exfoliation pans in lesotho southern africa climate process morphological linkages abstract although alpine pans have been reported from a variety of mountain regions these have received limited research attention and are thus amongst the least known of closed basins this study investigates macro and fine scale morphological attributes and the process dynamics of alpine turf exfoliation pans in the high drakensberg of lesotho southern africa climate data temperature precipitation and wind are used to better ascertain climate surface process linkages and how these may be associated with the observed morphological phenomena thirty pans were assessed for both macro and fine scale aspect controlled morphological attributes during 2005 tinytag temperature loggers recorded ground temperatures on various pan riser aspects to establish the potential for cryogenic activity similarly wind speed and direction data from 2001 were used to identify the potential role of wind as an erosion and transportation mechanism the number and total weight of detached turf clumps accumulated at the base of various pan riser aspects were determined in july 1999 september 2001 and september 2004 it is suggested that the pans originated through initial turf disruption by animal trampling and turf burning followed by the cryogenic up heave of sediments the pans typically elongate towards the southeast as they enlarge demonstrate most active erosion on eastern and southeastern riser aspects and host seasonal micro echo and micro climbing dunes along such riser aspects it is concluded that an annual cyclic seasonal pattern of contemporary climate driven geomorphic processes dominated by strong northwesterly winds control the fine scale morphological evolution of alpine turf exfoliation pans in the lesotho highlands

gravity evidence of very thin crust at the gakkel ridge arctic ocean abstract gakkel ridge the active spreading center in the arctic ocean is the slowest spreading portion of the global mid ocean ridge system total spreading rates range from 0 6 cm yr in the east where the ridge disappears beneath the laptev shelf to 1 3 cm yr in the west near greenland bathymetry and gravity surveys of four sections of the gakkel ridge were carried out in 1996 by the u s navy nuclear submarine uss pogy as part of scicex 96 in order to sample variations in seafloor morphology and gravity anomalies as a function of spreading rate the ridge axis throughout the survey area is characterized by a continuous axial rift valley similar to that observed at other slow spreading ridges the continuous rift axis suggests that well organized seafloor spreading is occurring at total spreading rates of less than 1 cm yr in three faster spreading 1 13 1 24 cm yr western survey areas located between 7 e and 54 e the gakkel ridge is deep compared with other ridge axes axial depths range between 4600 and 5100 m and ridge flanks at about 3200 m the ridge flank morphology is very blocky and is characterized by large scarps and deep fault bounded troughs very large amplitude free water anomalies with peak to trough amplitudes of 85 150 mgal are observed centered on the axis of the gakkel ridge modeling of the free water anomalies by varying the crustal thickness and average crustal density including the gravity effect of the cooling of the mantle away from the axis implies that if the average crustal density is less than 2900 kg m3 the crustal thickness must be less than 4 km the axial rift valley at the fourth survey area near 98 e where the total spreading rate is 0 99 cm yr is buried by sediments the axis in this region is associated with a continuous 70 mgal gravity minimum implying the presence of a large buried rift valley the rift flanks at 95 e are at a depth of greater than 3800 m 600 m deeper than the average depth at the gakkel ridge axis west of 60 e simple isostatic calculations suggest that the crust in this region may be vanishingly thin beneath the sediment cover these observations indicate a relationship between melt production and seafloor spreading rate at very slow spreading rates suggesting that ultra slow spreading may suppress melt production or delivery at the gakkel ridge

a 40 000 yr pollen and diatom record from lake tritrivakely madagascar in the southern tropics abstract links between southern and northern hemisphere climates during the late quaternary are poorly known partly due to the scarcity of continuous climatic records in the southern tropics pollen and diatom evidence from lake tritrivakely 19 47 s provides information on vegetational and hydrological changes in the central highlands of madagascar over the past 40 000 yr most of the record reflects natural environmental variability since humans arrived on the island ca 2000 yr b p during glacial times the migration of mountain plants toward lower altitudes is consistent with a temperature decrease and with reduced atmospheric co2levels in the lake a positive mean annual hydrologic balance from 38 000 to 36 000 and from 17 500 to 9800 cal yr b p coincided with periods of decreasing summer insolation and preceded by several millennia lake rises in the northern tropics a negative hydrologic budget during periods of maximum seasonal contrast in solar radiation is partly attributed to high summer evaporation rate the last glacial maximum was cool and dry the deglacial warming occurred in two steps the first step accompanied by an increase in wetness occurred abruptly at ca 17 000 cal yr b p about two millennia earlier than in the northern hemisphere it is abundantly documented in southern terrestrial data the second step at 15 000 cal yr b p was in phase with the first major temperature change in the northern hemisphere

slope geometry design as a means for controlling rockfalls in quarries this paper presents a rockfall control method for rock quarries based on benched rock slope design and catch bench width control the aim is to prevent rockfalls in quarries which cause a significant number of accidents and even fatalities whereas catch ditches have traditionally been used as the main rockfall control method for roads and highways benches carved into slopes are typically used in open pit mining in the road engineering field a simple empirical technique recently reviewed and updated has long been in use that is capable of ensuring slope designs that prevent falling rocks from reaching the travelled area of a road such techniques are lacking in the quarrying field however and this work is an attempt to develop a method similar to those developed for road engineering but specifically adapted to quarry slope geometries using statistically significant data on the parameters affecting falling block trajectories obtained from empirical data and from a back analysis performed using a rockfall modelling code we estimated geometries for quarry slopes that would prevent falling rocks from reaching work areas this information was compiled and presented in the form of charts for 2 bench 5 bench and 8 bench slopes that enable the user to design rockfall safe slopes

stable isotope evidence of late mis 3 to middle holocene palaeoenvironments from sehonghong rockshelter eastern lesotho evidence for human occupation of southern africa s high altitude maloti drakensberg mountains is surprisingly common in the last glacial yet the attraction of this relatively severe cold region for hunter foragers remains unclear sehonghong rockshelter 1870 m asl in the eastern lesotho highlands provides evidence for human occupation spanning marine isotope stage 3 through the late holocene excellent organic preservation provides opportunities for establishing multiple palaeoenvironmental proxy records to address this conundrum in high altitude zones the proportions of c3 and c4 plants archived in soil organic matter and faunal enamel provide sensitive indicators of past temperature shifts we first extended the radiocarbon chronology to ca 35 ka using abox sc radiocarbon dates of charcoals next we analysed stable isotopes in soil organic matter from the sedimentary sequence and in faunal tooth enamel from the newly dated lower strata the results suggest predictably that c3 vegetation and low temperatures prevailed until early warming at ca 15 ka with a series of sharp shifts thereafter low values for 13c and 18o in faunal enamel ca 33 ka suggest a negative temperature excursion at this time and potentially greater precipitation as snowfall in the highlands compared with lower altitudes

assessment of rockfall potential in the kula manisa turkey geopark region the term geopark is an interrelated phenomenon of geology landscape civilisation and society one of the first geopark areas in turkey will be founded in the kula district of manisa this region is an impressive area with its archaeological historical and tourism related features and its geological characteristics such as cinders and maars tectonic structures and earth pillars moreover the earth pillars in the region present high rockfall potential due to their geometric and lithologic peculiarities formed by erosional processes the present study aims in investigating the rockfall potential in this area by means of experimental investigation and numerical analyses extensive field studies including determination of earth pillar locations with rockfall potential geological description of the earth pillars scan line surveys on discontinuities identification of slope profiles measurement of actual fallen block dimensions and sampling procedures were carried out the eight earth pillar profiles were analysed to determine the run out distances of basalt blocks and seven blocks were found to be capable of reaching the transportation line for future protection purposes barrier designs were suggested by computer analyses additional analyses were performed to determine rockfall prone areas taking into consideration the mapped rockfall source areas based on these analyses the transportation line is threatened by potential rockfall these results are in accordance with conclusions of the runout distance analyses as a consequence environmental aspects and rockfall phenomenon of the kula geopark region must be taken into consideration during the planning process it should also be pointed out that we have to own the values of geological heritages and to protect them based on the scientific and rational approaches

coseismic ground deformation of the 6 april 2009 l aquila earthquake central italy mw6 3 1 we provide field data of coseismic ground deformation related to the 6 april mw 6 3 l aquila normal faulting earthquake three narrow fracture zones were mapped paganica colle enzano p e mt castellano mt stabiata c s and san gregorio sg these zones define 13 km of surface ruptures that strike at 130 140 we mapped four main types of ground deformation free faces on bedrock fault scarps faulting along synthetic splays and fissures with or without slip that are probably due to the near surface lithology of the fault walls and the amount of slip that approached the surface coseismically the p e and c s zones are characterized by downthrow to the sw up to 10 cm and opening up to 12 cm while the sg zone is characterized only by opening afterslip throw rates of 0 5 0 6 mm day were measured along the paganica fault where paleoseismic evidence reveals recurring paleo earthquakes and post 24 8 kyr slip rate 0 24 mm yr

the 1995 grevena northern greece earthquake fault model constrained with tectonic observations and sar interferometry after the 1995 grevena ms 6 6 event in northern greece we mapped the earthquake fault break in detail the surface break is small 8 12 km long 4 cm slip compared to the moment release of the event however the morphologic and tectonic study of the active faults in the field and using the spot satellite imagery suggests that the earthquake ruptured part of a much larger fault system including interconnecting segments we used sar interferometry of the satellite ers 1 imagery to characterize the coseismic displacement field this shows a kidney shaped zone of subsidence reaching 30 cm flanked by an uplift zone reaching 5 cm we reproduce this field using dislocations in an elastic half space and our observations of the fault system this requires 1 m slip from 4 to 15 km depth on a main normal fault segment dipping nnw our preliminary model includes significant ne dipping scissors faulting at the eastern end of the rupture clearly seen in the interferograms

predominance of unilateral rupture for a global catalog of large earthquakes the manner in which an earthquake rupture propagates across a fault reflects both the initial properties of the fault and the dynamical stresses produced by the rupture we quantify the propagation of an earthquake rupture using the second moments of the earthquake space time distribution in particular the second moments provide a simple way to differentiate between approximately bilateral and predominantly unilateral ruptures we determined the second moments for a catalog of m w 7 earthquakes that have occurred since 1994 the results show that approximately 80 of large shallow ruptures are predominantly unilateral our result agrees well with strong motion inversions from previous studies on moderate and large earthquakes the predominance of unilateral propagation in large earthquakes is explained by a simple characteristic earthquake model in which large events rupture an entire structurally defined fault segment and nucleation points are uniformly distributed along the fault the predominance of unilateral rupture may also be enhanced by the dynamic stress field produced by contrasts in the elastic properties between the two sides of plate boundary faults manuscript received 16 november 2001

paleo environment and flooding of the limpopo river plain mozambique between c ad 1200 2000 multi proxy analysis was performed on a radiocarbon dated core collected from a relic oxbow lake in the limpopo river plain mozambique with the aim to reconstruct paleo environment and past flooding of the lower river system over the past c 800 years an additional objective was to evaluate and investigate the potential use of different proxies as recorders of paleo flooding events and paleo environmental variability within the floodplain the proxies applied in this study were mineral magnetic properties grain size distribution organic carbon content and diatom microfossil assemblages we found that sediment grain size and mineral magnetic properties of the minerogenic fraction were the most sensitive proxies in terms of detecting signals from high intensity river discharge events in the 800 year long sequence variations in sand content magnetic susceptibility and saturation isothermal remnant magnetization suggest at least four major flooding events at the site during the reconstructed period in the mid 1200 late 1300 mid 1500 ad and during the last century the diatom proxy reflects the development of the site from an open oxbow lake to a mainly terrestrial area the diatom assemblage indicates that open lake conditions prevailed at the site between c ad 1200 1400 with periodic inundation by marine water most likely due to late holocene sea level changes from c ad 1400 and onwards diatoms were rarely deposited at the site which indicates drier conditions this was a result of soil formation and gradual in filling of the lake a process which possibly was accentuated by a regionally dry climate situation our study shows that oxbow lakes and the proxies used here have great potential for reconstructing flooding events a knowledge that is crucial for potential prediction and mitigation of flooding events in mozambique in the future although chronological uncertainties limit comparisons to other paleo environmental records it seems that the flooding events recorded at our site occurred both during regionally wet and dry periods our data infer however that flooding was probably more clearly recorded during the lake stages than during infilled stage probably as the terrestrial environment was more exposed to erosion c 2014 elsevier b v all rights reserved less

high resolution palaeoclimatology of the last millennium a review of current status and future prospects this review of late holocene palaeoclimatology represents the results from a pages clivar intersection panel meeting that took place in june 2006 the review is in three parts the principal high resolution proxy disciplines trees corals ice cores and documentary evidence emphasizing current issues in their use for climate reconstruction the various approaches that have been adopted to combine multiple climate proxy records to provide estimates of past annual to decadal timescale northern hemisphere surface temperatures and other climate variables such as large scale circulation indices and the forcing histories used in climate model simulations of the past millennium we discuss the need to develop a framework through which current and new approaches to interpreting these proxy data may be rigorously assessed using pseudo proxies derived from climate model runs where the answer is known the article concludes with a list of recommendations first more raw proxy data are required from the diverse disciplines and from more locations as well as replication for all proxy sources of the basic raw measurements to improve absolute dating and to better distinguish the proxy climate signal from noise second more effort is required to improve the understanding of what individual proxies respond to supported by more site measurements and process studies these activities should also be mindful of the correlation structure of instrumental data indicating which adjacent proxy records ought to be in agreement and which not third large scale climate reconstructions should be attempted using a wide variety of techniques emphasizing those for which quantified errors can be estimated at specified timescales fourth a greater use of climate model simulations is needed to guide the choice of reconstruction techniques the pseudo proxy concept and possibly help determine where given limited resources future sampling should be concentrated

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

in situ rockfall testing in new south wales australia abstract despite the significance of rockfall hazards in australia this phenomenon is still poorly characterised in many regional environments in particular the relationship between slope rock properties and rockfall motion parameters needs better definition in the context of rockfall prediction it is important to quantify the normal and tangential restitution coefficients referred to as k n and k t and the equivalent rolling coefficient which are site specific several series of rockfall tests have been conducted in three different geological environments in new south wales the results of the tests show a large variability of the motion parameters which is due to the natural variability of the blocks and to the randomness of the impact positions also values of k n consistently and systematically higher than the benchmark values from the literature have been inferred despite there being no clear correlation between the restitution coefficients and the rotational energy rotational phenomena are believed to be at the origin of such results

a 19 5 kyr vegetation history from the central cederberg mountains south africa palynological evidence from rock hyrax middens abstract in arid and semi arid areas such as southern africa rock hyrax procavia capensis middens represent an exceptionally valuable source of late quaternary palaeoenvironmental information pollen and stable isotope data derived from two rock hyrax middens extracted from de rif in the cederberg mountains of the southwestern cape casts new light on climatic changes that occurred across the last glacial interglacial transition lgit and the holocene 19 5 0 7 cal kbp and how the region s vegetation responded to these changes significant changes in vegetation community composition would be expected in response to environmental changes characteristic of the contrast between glacial and interglacial climates however the pollen assemblages in general indicate that mountain fynbos remained dominant throughout the record and that most of the pollen taxa exhibited only muted frequency variations this finding could be considered to be inconsistent with indications of marked climatic variations recorded in the stable isotope records for the same midden an analysis of the geological setting and the bioclimatic affinities of the taxa suggest that the explanation for this inconsistency may lie in the dominating influence of sandstone substrates and the relative resilience of mountain fynbos vegetation to climate change

space time distribution of afterslip following the 2009 l aquila earthquake 1 the inversion of multitemporal dinsar and gps measurements unravels the coseismic and postseismic afterslip slip distributions associated with the 2009 mw 6 3 l aquila earthquake and provides insights into the rheological properties and long term behavior of the responsible structure the paganica fault well resolved patches of high postseismic slip 10 20 cm appear to surround the main coseismic patch maximum slip 1 m through the entire seismogenic layer above the hypocenter without any obvious depth dependent control time series of postseismic displacement are well reproduced by an exponential function with best fit decay constants in the range of 20 40 days a sudden discontinuity in the evolution of released postseismic moment at 130 days after the main shock does not correlate with independent seismological and geodetic data and is attributed to residual noise in the insar time series the data are unable to resolve migration of afterslip along the fault probably because of the time interval six days between the main shock and the first radar acquisition surface fractures observed along the paganica fault follow the steepest gradients of postseismic line of sight satellite displacements and are consistent with a sudden and delayed failure of the shallow layer in response to upward tapering of slip the occurrence of afterslip at various levels through the entire seismogenic layer argues against exclusive depth dependent variations of frictional properties on the fault supporting the hypothesis of significant horizontal frictional heterogeneities and or geometrical complexities we support the hypothesis that such heterogeneities and complexities may be at the origin of the long term variable behavior suggested by the paleoseismological studies rupture of fault patches with dimensions similar to that activated in 2009 appears to have a 500 year recurrence time interval documented by paleoseismic and historical studies in addition to that paleoseismological evidence of large 0 5 m coseismic offsets seems to require seismic events recurring every 1000 2000 years characterized by 1 multisegment linkage 2 surface ruptures larger than in 2009 and 3 complete failure of the 2009 coseismic and postseismic patches

sedimentary sequences at sani top lesotho highlands southern africa detailed examination of sediments retained in two north facing cirques south of sani top latitude 29 30 s longitude 29 2 e has been undertaken as a contribution to the late quaternary history of highland lesotho the sediments are exposed by gullies incised through the deposits nine sections are discussed in detail inorganic sediments matrix supported diamictons and derived orange gravels as well as organic dark clays and peats are present eight dated organic samples range in age from 13490bp currently the oldest organic carbon date from highland lesotho to 2310 bp the sedimentary sequences are interpreted to present a sequence of late quaternary events with climatic implications

quantification of climate change for the last 20 000 years from wonderkrater south africa implications for the long term dynamics of the intertropical convergence zone abstract in southeast africa a region for which few palaeoenvironmental records are available the fossil pollen record from the wonderkrater spring mound has contributed substantially to our understanding of past vegetation change since the last glacial maximum lgm 21 ka multivariate analysis of the pollen data by scott and thackeray 1987 provided environmental reconstructions suggesting relatively mesic lgm conditions with warm and dry conditions during the early holocene 11 6 cal kbp this conforms to predicted patterns of precipitation change in the southern african tropics in response to northern hemisphere cooling and orbital forcing subsequent data from the cold air cave speleothems and a sea surface temperature record from the mozambique channel however indicate that conditions during the early to mid holocene may have been wetter than present in the wonderkrater region to explore this question further we have created a series of botanical climatological transfer functions based on a combination of modern climate and plant distribution data from southern africa applying these to the wonderkrater fossil pollen sequence we have derived quantitative estimates for temperatures during the cold and warm quarters as well as precipitation during the wet and dry quarters in addition a species selection method based on bayesian statistics is outlined which provided a parsimonious choice of likely plant species from what are otherwise taxonomically broad pollen types we do not propose that our findings invalidate the previous principal component analyses but they do have the advantage of being based more clearly on the relationship between modern plant distributions and individual climatic variables results indicate that temperatures during both the warm and cold seasons were 6 2 c colder during the lgm and younger dryas and that rainy season precipitation during the last glacial maximum was 50 of that during the mid holocene our results also imply that changes in precipitation at wonderkrater generally track changes in mozambique channel sea surface temperatures with a steady increase following the younger dryas to a period of maximum water availability at wonderkrater 3 7 ka these findings argue against a dominant role of a shifting intertropical convergence zone in determining long term environmental trends and indicate that the northern and southern tropics experienced similar climatic trends during the last 20 kyr

experimental studies on fragmentation of rock falls on impact with rock surfaces rock fall is a common natural hazard causing significant damage to infrastructure and loss of life rock fragmentation is frequently observed during rock fall events and several authors have raised issues related to the impact of fragments on the protection structure however this phenomenon is not accounted for when designing the protection barriers the paper presents the results of 20 rockfall tests performed in a quarry in italy to provide new insight into the fragmentation phenomenon especially in the case of foliated materials the results have shown that the impacting angle plays a key role in the fragmentation of foliated rocks whereas the effect of the impacting energy tends to be of second order no threshold in impacting energy could be defined to explain what triggers the fragmentation it has been noticed that the proportion of impacting energy dissipated during fragmentation is relatively constant and depends on the choice of the normal restitution coefficient

stable carbon isotopic evidence for climate change across the late pleistocene to early holocene from lesotho southern africa although significant environmental and climatic changes are likely to have occurred across the pleistocene holocene transition in southern africa records are sparse with information regarding temperature change especially rare we thus know little about the conditions facing later stone age human populations at this time particularly those in the highland interior where temperature shifts would have had strong impacts on floral and faunal distributions in lesotho a well defined altitudinal distribution of c3 and c4 photosynthetic plant taxa and their remains in soil organic matter provides a means of estimating past temperature shifts we applied this principle to stratified sediments from two archaeological sequences in the lesotho lowlands c 1600 m a s l to produce a palaeotemperature record focusing on the period 14 000 9500 cal a bp the results show an overall trend from exclusively c3 vegetation at the last glacial maximum towards greater contributions of c4 taxa and thus warmer conditions during the holocene however large temperature fluctuations are evident within this trend with rapid changes of up to 4 c visible between 11 200 and 9500 cal a bp the continued presence of hunter gatherers during this time suggests that the region must have remained attractive to human populations despite significant climatic instability and cool episodes copyright 2013 john wiley sons ltd

evidence for holocene sea level change at verlorenvlei western cape south africa abstract a series of sediment cores extracted from what is today a large freshwater coastal lake verlorenvlei has been sub sampled radiocarbon dated and subjected to a range of palaeoenvironmental techniques in particular pollen analysis sedimentology and geochemistry a mid late holocene higher sea level is evident in the cores indicating the rapidity with which sea level change can occur and invoke other forms of environmental response following a hiatus in sedimentation most probably around 3800 bp the marine conditions at the site were replaced by fresh water as the dominant hydrological and ecological influence laminated organic sediments in some of the cores suggest that around 300 years ago a fresh water lake characterised verlorenvlei since then the picture revealed by high resolution palynology is one of progressive levels of human disturbance both in and around the study area sedimentological and palaeoecological analyses of additional cores from the vlei two from the distal inland and one from the proximal coastal end of the system serve further to elucidate the precise nature of sea level change in the late holocene and facilitate the construction of a refined holocene sea level curve for the region environmental changes in the late holocene are shown to be especially dynamic

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

reconstruction of environmental and climate changes at braamhoek wetland eastern escarpment south africa during the last 16 000 years with emphasis on the pleistocene holocene transition abstract a paleo environmental record covering the last 16 ka 16 000 cal yrs bp from the eastern areas of the summer rainfall region in south africa is presented this area is until now sparsely investigated due to the lack of well preserved natural archives for this study we used a peat section from a wetland situated close to the drakensberg escarpment where the high annual rainfall amounts supported a continuous peat accumulation since c 16 ka one peat core was analysed in terms of fossil pollen composition carbon and nitrogen content isotope composition 13c 15n and microscopic charcoal concentration the greatest degree of temporal resolution was achieved from the late pleistocene and early holocene section where proxy records indicate relatively dry conditions between ca 16 13 7 ka 12 8 10 5 ka 9 5 8 2 ka and wet conditions between c 13 7 12 8 ka and 10 5 9 5 ka a weak moisture signal is also evident at c 8 2 7 5 ka the late pleistocene to early holocene period was relatively cool while conditions became generally warmer after 11 8 ka the interpretation of the mid and late holocene sequence is limited due to a slow accumulation and low sample resolution but the available data suggest relatively dry conditions until c 1 5 ka followed by more humid conditions until c 0 5 ka we suggest that the millennial scale variability within the record can be attributed to shifts in the circulation systems dominating the region i e the latitudinal movements of the inter tropical convergence zone itcz and the dynamics of the mid latitude low pressure belts

extension on the tibetan plateau recent normal faulting measured by insar and body wave seismology we use insar and body wave modelling to determine the faulting parameters for a series of five mw 5 9 7 1 normal faulting earthquakes that occurred during 2008 including the march 20 yutian earthquake mw 7 1 one of the largest normal faulting events to have occurred recently on the continents we also study three earlier normal faulting earthquakes that occurred in southern tibet between 1992 and 2005 coseismic deformation for each of these eight events is measured with ascending and descending interferograms from envisat ers and alos sar data elastic dislocation modelling of the line of sight insar displacements and body wave seismological modelling of p and sh waves are used to estimate fault parameters and are found to be in good agreement for all the events studied the use of insar to measure deformation allows a relatively precise determination of the fault location in addition to resolving the focal plane ambiguity only five of the eight events are associated with a clear surface topographic feature suggesting that an underestimation of the amount of extension would result from using the surface expressions of normal faulting alone the observations in all cases are consistent with slip on planar surfaces with dips in the range 40 50 that penetrates the uppermost crust to a depth of 10 15 km we find no evidence for active low angle dip less than 30 normal faulting the contribution of the normal faulting to overall extension estimated by summing seismic moments over earthquakes for the past 43 yr is 3 4 mm yr 1 or 15 20 per cent of the rates of extension measured across the plateau using gps 85 per cent of the moment release in normal faulting over the past 43 yr has occurred in regions whose surface height exceeds 5 km this observation adds weight to the suggestions that the widespread normal faulting on the plateau is the result of variations in the gravitational potential energy of the lithosphere

seismological constraints on the down dip shape of normal faults this work forms part of the nerc and esrc funded project earthquakes without frontiers and was partially supported by the nerc large grant looking inside the continents from space

late quaternary environmental changes from a pollen and diatom record in the southern tropics lake tritrivakely madagascar abstract a pollen and diatom study of a 40 m sedimentary sequence from lake tritrivakely in the central highlands of madagascar provides evidence for climatic and environmental changes during the late pleistocene and the holocene the major features of the modern regional climate and vegetation distribution and the hydrological characteristics of the lake basin are first summarized lithological units and specific methods used to establish the pollen and the diatom biozones are then presented the chronology of the upper 13 m of the sequence 0 41 kyr is supported by ams radiocarbon dates it has not been possible to acquire absolute ages for the lower 27 m of the core however a tentative age model based on comparisons between the terrestrial pollen and the vostok d isotopic temperature records suggests an age of about 150 kyr for the core base the vegetation primarily responded to variations in temperature six major cold warm cycles are identified during the cold phases ericaceous bush surrounded the site assuming that the age model is correct cold phases prior to 143 115 110 94 88 75 69 and 22 17 kyr coincide with periods of high local summer insolation the warm phases are of different amplitude they show first the development of a wooded grassland under a dry climate which may coincide with periods of low summer insolation around 125 100 83 60 and 10 5 kyr and then the growth of mid latitude trees under wetter conditions the diatom record primarily documents changes in the precipitation minus evaporation balance p e in the lake catchment which appear consistent with orbitally induced changes in p and seasonal contrasts as suggested by our pollen based age model and the 14c dated section of the record an overall trend from a relatively deep nutrient rich lake to a shallow oligotrophic peat marsh is partly attributed to the basin infilling however wet dry oscillations are superimposed over this trend the two first lake high stands before 143 and around 115 kyr if the age model is correct and low stands around 125 and 105 kyr match pollen inferred cold and warming phases respectively later periods of low p e also fit cold phases and occur apparently every 12 10 kyr summer rain during phases of high summer insolation was not heavy enough to compensate for the large evaporation evapotranspiration losses during warm summers and dry winters especially during the cold last glacial maximum which was drier than today

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

interhemispheric dynamics of the african rainbelt during the late quaternary abstract the spatial pattern of precipitation variability in tropical and subtropical africa over the late quaternary has long been debated prevailing hypotheses variously infer 1 insolation controlled asymmetry of wet phases between hemispheres 2 symmetric contraction and expansion of the tropical rainbelt and 3 independent control on moisture available in southern africa via sea surface temperatures in the indian ocean in this study we use climate model simulations covering the last glacial cycle 120 kyr with hadcm3 and the multi model ensembles from pmip3 the palaeoclimate model intercomparison project to investigate the long term behaviour of the african rainbelt and test these simulations against existing empirical palaeohydrological records through regional model data comparisons we find evidence for the validity of several hypotheses with various proposed processes occurring concurrently but with different regional emphasis e g asymmetric shifts at the seasonal extremes and symmetric expansions contractions towards west equatorial regions crucially variations in rainfall are associated with multiple forcing mechanisms that vary in their dominance both spatially and temporally over the glacial cycle an important consideration when interpreting and extrapolating from often relatively short palaeoenvironmental records

rupture history of the 2009 l aquila italy earthquake from non linear joint inversion of strong motion and gps data 1 we image the rupture history of the 2009 l aquila central italy earthquake using a nonlinear joint inversion of strong motion and gps data this earthquake ruptured a normal fault striking along the apennines axis and dipping to the sw the inferred slip distribution is heterogeneous and characterized by a small shallow slip patch located up dip from the hypocenter 9 5 km depth and a large deeper patch located southeastward the rupture velocity is larger in the up dip than in the along strike direction this difference can be partially accounted by the crustal structure which is characterized by a high velocity layer above the hypocenter and a lower velocity below the latter velocity seems to have affected the along strike propagation since the largest slip patch is located at depths between 9 and 14 km the imaged slip distribution correlates well with the on fault aftershock pattern as well as with mapped surface breakages

evolving southwest african response to abrupt deglacial north atlantic climate change events abstract climate change during the last deglaciation was strongly influenced by the bipolar seesaw producing antiphase climate responses between the north and south atlantic however mounting evidence demands refinements of this model with the occurrence of abrupt events in southern low to mid latitudes occurring in phase with north atlantic climate improved constraints on the north south phasing and spatial extent of these events are therefore critical to understanding the mechanisms that propagate abrupt events within the climate system we present a 19 400 year multi proxy record of climate change obtained from a rock hyrax midden in southernmost africa arid anomalies in phase with the younger dryas and 8 2 ka events are apparent indicating a clear shift in the influence of the bipolar seesaw which diminished as the earth warmed and was succeeded after 14 6 ka by the emergence of a dominant interhemispheric atmospheric teleconnection

connecting seismically active normal faults with quaternary geological structures in a complex extensional environment the colfiorito 1997 case history northern apennines italy 1 the northern apennines of italy are characterized by a complex tertiary tectonic history where superposed compressional and extensional deformation occurred in such regions characterized by low active extensional strain rate the coseismic surface ruptures are rare and often a matter of much debate resulting in a difficult connection between geological faults i e faults which can be mapped at the surface and seismological faults i e faults which actually generate earthquakes the availability of detailed geological mapping and high resolution seismological data for the colfiorito area struck in 1997 by a sequence of six 5 mw 6 normal faulting earthquakes allow us to compare and verify the existence of geometric and kinematic correspondence between the mapped geological quaternary faults and the activated structures in map view the earthquakes distribution reflects the fault pattern mapped at the surface the length of activated and mapped faults is quite similar 7 10 km the coseismic subsided region imaged by interferometric synthetic aperture radar data is located in the hanging wall of the mapped normal faults that bound the quaternary basins in section view there is a geometric connection between mapped normal faults and the aftershock alignments used to image fault geometry at depth comparison of striated fault planes and aftershock focal mechanism solutions show a strong kinematic consistency this study points out that the quaternary tectonosedimentary evolution and the present day geological and geomorphologic setting of the colfiorito area can be interpreted as the result of repeated extensional earthquakes similar to the 1997 events occurring on nw se trending normal faults our data also show that the main shocks of the colfiorito sequence nucleated close to the intersections between the normal faults and the preexisting compressional transpressional structures which in 1997 acted as lateral barriers to rupture propagation and consequently constrained the fault size

fault rupture process of the 20 september 1999 chi chi taiwan earthquake we modeled the source rupture process of the 20 september 1999 chi chi taiwan earthquake mw 7 6 using an integrated dataset of near field strong ground motion and global positioning system observations this large inland thrust earthquake produced a surface break more than 80 km long along the chelungpu fault the event triggered over 700 strong motion instruments on the island of tai wan this large ground motion dataset provides the best opportunity to date to un derstand earthquake source processes in a major earthquake first we develop a 3d curved fault model consistent with the surface rupture data and aftershock distribu tion the subsurface fault plane has an average dip of 30 to the east and measures 96 km along strike and 40 km down dip next we applied a genetic algorithm to reconstruct the source rupture process the inversion results indicate a complex slip distribution with a generally broad triangular shaped slip zone that points down dip most of the displacement occurred over a 15 km depth range in the northern segment of the fault with the maximum slip exceeding 20 m the average slip is 3 8 m and the average rupture velocity is 2 6 km sec the mainshock slip distribution clearly complements the aftershock location distribution slip rise times range from 8 to 6 sec over most of the primary slip area and decrease slightly as rupture propagates south to north this relatively long rise time resulted in a low dynamic stress drop and low peak ground accelerations observed at surface stations the rake angle rotates across the rupture plane from predominantly dip slip in the southern segment to mostly left lateral oblique slip in the north we find that geometrical irregularities over the fault plane played an important role in controlling the temporal rupture behavior at fault bends rupture tends to decelerate the rake angle rotates to a near dip slip orientation and the shear stress increases as rupture tries to overcome the bending barriers the total seismic moment from our inversion is 2 9 10 27 dyne cm in good agreement with the harvard and the u s geological survey moment estimation

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

moment tensor analysis of the central italy earthquake sequence of september october 1997 the larger earthquakes in the umbria marche central italy seismic sequence of september october 1997 are analyzed using long period seismograms from the mediterranean seismographic network mednet and additional data from the global seismographic network gsn we modify the harvard centroid moment tensor cmt algorithm to allow moment tensor inversion of long period waveforms primarily rayleigh and love waves for small earthquakes at local to regional distances 5 5 in the sequence moment tensors have previously been determined using teleseismic waveforms and standard methods of analysis our results agree well with those of earlier studies we determine additional moment tensors for the largest foreshock and 10 aftershocks with mw 4 2 the earthquakes are characterized by normal faulting mechanisms with a ne sw tension axis and the presumed fault plane dips towards the sw only one of the fourteen events studied has a different faulting geometry indicating instead right lateral strike slip faulting on a plane oriented approximately e w or left lateral faulting on a plane oriented n s the september 26 mainshock 09 40 ut accounts for only approximately 50 of the total moment release in the sequence

holocene palaeoenvironments inferred from a sedimentary sequence in the tsoaing river basin western lesotho abstract the paper presents a sedimentological palynological and phytolith record from a 13 m deep holocene sedimentary sequence located in the tsoaing river valley southwestern lesotho six conventional radiocarbon and two ams dates provide a relatively high resolution holocene record for the sedimentary sequence ranging from ca 12 000 to 4000 years bp pollen is absent in the upper section but present in the lower 2 m confirming terminal pleistocene holocene conditions reported in previous published pollen and charcoal records from the region the absence of pollen in the upper layers of ca 9000 years bp and younger suggests that conditions over southwestern lesotho throughout much of the holocene was typified by a seasonal climate that prevented long term preservation of plant remains although other plant material like robust spores microscopic charcoal and phytoliths withstood oxidation sedimentological and phytolith results suggest that the period from ca 8600 to 8450 years bp experienced rapid environmental change towards drier conditions phases of chemical disintegration with organic input including local swamp phytoliths are suggested at ca 7000 years bp and again after 4500 years bp

analysis of a blockstream in the northern lesotho drakensberg southern africa abstract blockstreams are found in many mountain ranges worldwide and can be considered as an expression of the interplay between upslope sediment supply and transport limited capacity of slope sediment systems in mountain settings blockstreams have been most commonly described as periglacial landforms whose development and internal morphology reflect active layer processes and where the landforms are not active under present climatic conditions in the maloti drakensberg mountain range of eastern lesotho southern africa several blockstreams have been identified but their age evolution and relationships to climatic conditions are largely not known this study maps and analyses the properties of one large blockstream in the maloti drakensberg using field measurement techniques including schmidt hammer relative exposure age dating of blockstream boulders results show that the blockstream is a relict feature but debris may have been derived from several sources including from periglacial slope activity the presence of arcuate flow lobes within the main body of the studied blockstream attests to phases of slope driven boulder movement possibly controlled by active layer processes and cryoturbation or by slip at the base of the sediment body driven by seasonal water availability relative age data from schmidt hammer analysis suggest that different parts of the blockstream may have different ages and or sources by comparison with blockstreams elsewhere in the maloti drakensberg it is likely that it is of late quaternary and probably of local last glacial maximum age but younger holocene phases of activity cannot be excluded

development of active low angle normal fault systems during orogenic collapse insight from tibet active north trending rifts in tibet vary significantly in their character as a function of extension magnitude most rifts are characterized by internally drained basins bounded by high angle normal faults with paleogene or older rocks in the footwall however the central part of the yadong gulu rift near lhasa and the newly documented lunggar rift in west central tibet are bounded by low angle normal faults detachments with mylonitic rocks and miocene granites in the footwall and exhibit active basin incision and intrabasin topographic highs in areas of inferred maximum extension we suggest that tibetan rifts initiate as high angle normal fault and half graben or graben basin systems and evolve in response to increasing extension and footwall isostatic rebound into detachment systems that are active at uppermost crustal levels and above which rift basin fill is being uplifted and eroded

spatial and temporal variations in growth rates along active normal fault systems an example from the lazio abruzzo apennines central italy abstract the geometry kinematics and rates of active extension in lazio abruzzo italian apennines have been measured in order to gain a better understanding of the spatial and temporal variations in fault growth rates and seismic hazards associated with active normal fault systems we present fault map traces throws throw rates and slip directions for 17 parallel en echelon or end on active normal faults whose 20 40 km lengths combine to form a soft linked fault array ca 155 km in length and ca 55 km across strike throw rates derived from observations of faulted late glacial features and holocene soils show that both maximum throw rates and throw rate gradients are greater on centrally located faults along the strike of the array total throws and throw gradients show similar spatial variations but with weaker relationships with distance along strike when summed across strike throw rates are increasingly high towards the centre of the array relative to summed throws we interpret the above to suggest that throw rates have changed in the recent past ca 0 7 ma from spatially random fault growth rates initiating at 2 5 3 3 ma to growth rates that are greater on centrally located faults we interpret this as evidence for fault interaction producing throw rate variations that drive throw profile readjustment on these crustal scale soft linked faults the results are used to discuss seismic hazards in the region which are quantified in a second paper in this issue

microblock rotations and fault coupling in se asia triple junction sulawesi indonesia from gps and earthquake slip vector data the island of sulawesi eastern indonesia is located within the triple junction of the australian philippine and sunda plates and accommodates the convergence of continental fragments with the sunda margin we quantify the kinematics of sulawesi by modeling gps velocities and earthquake slip vectors as a combination of rigid block rotations and elastic deformation around faults we find that the deformation can be reasonably described by a small number of rapidly rotating crustal blocks relative to the sunda plate the southwestern part of sulawesi makassar block rotates anticlockwise at 1 4 myr the northeastern part of sulawesi the bangai sula domain comprises three blocks the central north sula block moves toward the nnw and rotates clockwise at 2 5 myr the northeastern manado block rotates clockwise at 3 myr about a nearby axis and east sulawesi is pinched between the north sula and makassar blocks along the boundary between the makassar block and the sunda plate gps measurements suggest that the trench accommodates 15 mm yr of slip within the makassar strait with current elastic strain accumulation the tectonic boundary between north sula and manado blocks is the gorontalo fault moving right laterally at about 11 mm yr and accumulating elastic strain the 42 mm yr relative motion between north sula and makassar blocks is accommodated on the palu koro left lateral strike slip fault zone the data also indicate a pull apart structure in palu area where the fault shows a transtensive motion and may have a complex geometry involving several active strands sulawesi provides a primary example of how collision can be accommodated by crustal block rotation instead of mountain building

influence of the ratio of planktonic to benthic diatoms on lacustrine organic matter δ13c from erlongwan maar lake northeast china carbon isotope ratio 13corg values of organic matter in lake sediments are commonly used to reconstruct environmental change but the factors which influence change are varied and complex here we report 13c values for sediments from erlongwan maar lake in northeast china in this record changes in 13c cannot be explained by simple changes in aquatic productivity instead values were likely influenced by differences in the ratio between planktonic and benthic algae as indicated by the remains of diatoms this is because the variation of 13corg in algae from different habitats is controlled by the thickness of the diffusive boundary layer which is dependent on the turbulence of the water compared with benthic algae which grow in relatively still water pelagic algae are exposed to greater water movement this is known to dramatically reduce the thickness of the boundary layer and was found to cause even more severe 13c depletion in erlongwan maar lake low values were linked to the dominance of planktonic diatoms during the period commonly known as the medieval warm period values gradually increased with the onset of the little ice age which we interpret as being driven by an increase in the proportion of benthic taxa due to effect of the colder climate the increase in planktonic diatoms at the end of the little ice age linked to higher temperature and a reduction in ice cover resulted in a further decline in 13corg

radiography of a normal fault system by 64 000 high precision earthquake locations the 2009 l aquila central italy case study 1 we studied the anatomy of the fault system where the 2009 l aquila earthquake mw 6 1 nucleated by means of 64 k high precision earthquake locations spanning 1 year data were analyzed by combining an automatic picking procedure for p and s waves together with cross correlation and double difference location methods reaching a completeness magnitude for the catalogue equal to 0 7 including 425 clusters of similar earthquakes the fault system is composed by two major faults the high angle l aquila fault and the listric campotosto fault both located in the first 10 km of the upper crust we detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops we observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays the width of the l aquila fault zone varies along strike from 0 3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution up to 1 5 km at the fault tips with an increase in the geometrical complexity these characteristics similar to damage zone properties of natural faults underline the key role of aftershocks in fault growth and co seismic rupture propagation processes additionally we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological i e creeping discontinuity explaining how normal faults detach at depth