copper mineralization prevented by arc root delamination during alpine himalayan collision in central iran contrasting geochemical signatures of copper ore hosting eocene and some barren undeformed miocene diorites to granites in central iran temporally overlap with the alpine himalayan collision and provide key implications on the existence and lack of cu mineralization during collisional magmatism high sr and low y and yb contents of eocene arc rocks in the natanz arc segment reflect thickened andean type orogenic arc crust 45 km whereas barren miocene natanz arc rocks 21 19 ma indicate thin arc crust similar to collisional volcanism in anatolia geochemical modeling indicates a change in the mineralogy of the melt residual from precollisional eocene basaltic garnet bearing 5 30 amphibolite to syn or postcollisional miocene metasomatized mantle peridotite which can be explained by collision induced delamination of the arc lithospheric root subsequent recharge of hot asthenosphere and melting of metasomatized mantle peridotite and lack of interaction with a garnet bearing arc crustal keel explain the low sr and high y and yb contents the relatively enriched initial sr isotope ratios of postcollisional miocene natanz rocks and the lack of copper mineralization in postcollisional miocene natanz arc rocks arc root delamination removes the copper and sulfur enriched metasomatized lithospheric arc root and hydrous cumulate reservoir required to form copper ore deposits lack of the dense melt residues also provides an alternative explanation for the elevated thin crustal iranian back arc plateau 38 km as a result of uplift by isostatic rebound rather than uplift by anomalous shortening miocene arc root delamination implies a minimum age of 21 ma for the alpine himalayan collision in central iran

weathering limited rainfall triggered shallow mass movements in undisturbed steepland tropical rainforest rainfall triggered landslides in undisturbed tropical rainforests may have been underestimated as contributors to slope development and denudation in the past theoretically ideal conditions for such geomorphic processes i e steep slopes and frequent high magnitude and intensity rainfall events occur in a number of tropical regions particularly within southeast asia therefore a high frequency of occurrence of shallow slope failures was expected in the undisturbed steeplands of southeast brunei stability conditions of the steep planar slopes were examined using a deterministic modelling approach in order to examine the possibility that most slopes could not fail in response to rainfall because they did not possess a sufficiently thick mantle of residual soil a simple hillslope hydrology model based on a soil moisture balance approach was used to simulate hillslope responses to measured and simulated rainfall events the stability of saturated slopes could then be analysed using the infinite slope model the input shear strength parameters for which were obtained from direct shear tests and then calibrated by back analysis of a failure which occurred in late 1991 the findings suggest that any slope of 40 and steeper should fail several times every year in response to storm events but that in reality most of the slopes have failed previously and have not yet regained a critical depth of residual soil some approximate values for rates of weathering and slope development suggest that any given slope will not fail at intervals of less than 10 000 years therefore the occurrence of shallow failures will be infrequent but nevertheless significant in terms of regional denudation and ecological diversity

state shifting at the edge of resilience river suspended sediment responses to land use change and extreme storms abstract the interaction of climate geomorphology and land use dictates catchment sediment production and associated river sediment loads accordingly the resilience of catchments to disturbances can be assessed with suspended sediment regimes this case study in the hill country of the lower north island of new zealand was a decade long examination of the short and long term effects of an extreme storm event on sediment supply and exhaustion in the oroua and pohangina catchments two catchments that have experienced intense land use changes and frequent broad scale landslides indicators of hydrologic alteration a program developed to characterize hydrologic regimes was used to analyze daily suspended sediment records over a period of a decade in order to characterize sediment regimes of the oroua and pohangina an aggregated data set of sediment bearing events for the period of record was analyzed to examine the suspended sediment response of individual storms relative to runoff magnitudes the findings of this study demonstrate that large storms that generate extreme landsliding and flooding have the ability to produce enough sediment to temporarily convert catchments from a supply limited state to a transport limited state landsliding and thus sediment supply was disproportionately high in locations where livestock grazing occurred on steep hillslopes the timing and intensity of previous storms or the antecedent catchment condition was also shown to influence the response of the catchments in both catchments suspended sediment loads were elevated for a period of 4 years following the landslide generating february 2004 storm the methods and findings we present are useful for assessing the resilience of catchments exposed to frequent disturbances such as land use changes and landslides

aftershocks of the andreanof islands earthquake of june 10 1996 and local seismotectonics three questions have been addressed in connection with an mw 7 7 earthquake that occurred in the andreanof islands alaska on june 10 1996 first was there any variation in seismic activity rate during the previous five years that might have been diagnostic of the imminent occurrence of this event the answer based on the usgs pde catalog is no second though there were abundant pre event earthquakes and aftershocks on both sides of adak canyon why was there very little activity under the canyon itself a property that has been observed previously it is not possible to resolve the cause of the behavior with existing seismological data finally how does one explain the eastern group of aftershocks which fell within the zone of abundant aftershocks of the 1986 mw 8 andreanof islands earthquake when very little of the 1996 mainshock moment was released under or to the east of adak canyon one explanation of these aftershocks is that the recent aftershocks are late aftershocks of 1986 whose occurrence within a short time was induced by the stress pulse but not seismic slip from the 1996 earthquake though large earthquakes in the aleutians occur in distinct tectonic blocks the boundaries of these blocks may not always be defined reliably by aftershock zones

buffers barriers and blankets the dis connectivity of catchment scale sediment cascades abstract catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency this paper introduces the concept of landform impediments termed buffers barriers and blankets that impede sediment conveyance by limiting the connectivity between landscape compartments buffers restrict sediment delivery to channels barriers inhibit sediment movement along channels and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment these features operate as a series of switches which turn on off processes of sediment delivery determining the effective catchment area at any given time using previously documented examples the role of these features in affecting the operation of sediment cascades in a low relief passive landscape setting such as the australian landmass is contrasted to examples from high relief uplifting settings in new zealand the australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since european settlement have impacted upon landscape sensitivity and prospects for river recovery this approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting

landslide occurrence as a response to land use change a review of evidence from new zealand abstract vegetation cover is an important factor influencing the occurrence and movement of rainfall triggered landslides and changes to vegetation cover often result in modified landslide behaviour however it is difficult to relate the occurrence of landslides directly to variations in land use especially in some european countries in contrast new zealand provides a good opportunity to investigate geomorphic responses to anthropogenic land cover changes before european settlers first arrived in the 1840s hilly regions were only marginally influenced by human activity the maoris new zealand s first settlers lived largely on coastal plains or near lakes and rivers they influenced general vegetation cover only through localized burning practices in contrast european settlers moved into the back country and converted extensive hill areas from native forest and bush to pasture this reduced the strength of the regolith and rendered the slopes more susceptible to landslides pulses of natural sedimentation in the pre european period have been related to volcanic activity climatic variability including changes in frequency of cyclonic storms and wind erosion and fluvial erosion following forest fires initiated either by volcanic eruptions or lightning strikes since european deforestation began sediment production has largely been determined by landslide events on unstable slopes thousands of landslides were triggered by high magnitude low frequency climatic events during storms with estimated return periods in excess of 50 years in contrast low magnitude high frequency rainfall events have caused gully and channel erosion examples from different parts of new zealand indicate changes in sediment generating processes following land use modifications after deforestation landslides have contributed significantly to sediment sequences in depositional basins such as lakes swamps estuaries coastal wetlands and the nearshore and offshore zones of continental platforms

signals of watershed change preserved in organic carbon buried on the continental margin seaward of the waipaoa river new zealand abstract holocene sediments buried on the continental shelf seaward of the waipaoa river northeastern new zealand preserve a stratigraphic record of terrestrial environmental change the well characterized long term record of storms volcanism and human disturbance in this region provides an opportunity to examine how such changes are reflected in the character of organic carbon oc buried on the continental margin complimentary evidence obtained from analyses of the 14 c content and the elemental and stable carbon isotopic composition of different sedimentary fractions including charcoal wood and clay sized isolates indicates that these perturbations led to mobilization of oc components with variable storage histories in the watershed charcoal transported in the modern waipaoa river and buried in offshore depocenters includes a highly aged component that has apparently been slowly released from storage in soil or alluvial terraces the charcoal fraction ages become dramatically younger in sediments deposited after the taupo volcanic eruption 1717 cal yr bp and then polynesian settlement ca 700 cal yr bp both signaling biomass burning the mean age of woody plant fragments and clay bound oc deposited on the shelf also varies over time with older material having accumulated in the middle holocene and since human occupation deposition of older than average wood fragments and clay bound oc between about 5 and 3 6 kyr bp correlates with evidence for a period of increased storm frequency in the region and may reflect the enhanced delivery of aged soil and sedimentary rock mobilized from hill slopes via earthflows and or deep seated landslides similarly the deposition of older wood and clay bound oc commensurate with the first anthropogenic disturbance ca 700 years ago is consistent with accelerated mass wasting due to deforestation at the same time a change in the elemental and stable isotopic composition of bulk and clay bound oc buried on the shelf may reflect increased marine primary productivity and or mobilization of oc from deep levels in soil profiles deforestation of the waipaoa headwaters by european settlers beginning in the middle 19th century is evinced by a sharper rise in the age of clay associated oc buried offshore today deep gully incision into fractured sedimentary bedrock is a major source of sediment and kerogen to the river and this process has left its mark on the age of sedimentary oc delivered to the adjacent margin

a source to sink perspective of the waipaoa river margin abstract a fundamental goal of the earth science community is to understand how perturbations on earth s surface are preserved in the stratigraphic record recent source to sink s2s studies of the waipaoa sedimentary system wss new zealand are synthesized herein to provide a holistic perspective of the processes that generate transport and preserve sedimentary strata and organic carbon on the waipaoa margin in the late quaternary rapid uplift associated with subduction processes and weak sedimentary units have conspired to generate rapid rates of incision and erosion in the waipaoa catchment since the last glacial maximum lgm we show that although much of the sediment exported offshore during this time interval originated from valley excavation a substantial portion emanated from hillslopes mostly through deep seated landslide and earthflow processes that were vigorous during periods of rapid fluvial incision just prior to the pleistocene holocene transition lacustrine sediments deposited in naturally dammed 7 ky old lake tutira provide a record of holocene environmental controls on upper catchment sedimentation in the wss with 1400 storms identified storm frequency is modulated by the waxing and waning of atmospheric teleconnections between the tropics and antarctica furthermore clear long term changes in sediment yield are evident from the lake tutira record following human settlement as conversion to pasture is accompanied by a 3 fold increase in the long term lake sediment accumulation rate whereas there is ample evidence that waipaoa river flood deposits are routinely deposited offshore in the sheltered confines of poverty bay over the longer term waves and currents subsequently resuspend and transport these deposits both landward sandy fraction and seaward finer fraction thus the timing of sediment supply to areas of net sediment accumulation is more often driven by wave events that are not associated with river flooding therefore we conclude that asynchronicity of river sediment delivery and of wave resuspension in most instances precludes the direct preservation of flood events in the stratigraphic record of the waipaoa shelf over the longer term the sediment package preserved on the shelf and slope since the lgm can be explained in large measure by sequence stratigraphic models forced by varying sea level and ongoing tectonic deformation of the margin as sea level rose sediment supply to the slope was reduced by about a factor of 5 due to shelf trapping despite this reduction turbidites are found at similar frequency throughout the lgm present as the dominant trigger appears to be subduction earthquakes with large ones having a return interval of about 200 100 years sediment budget exercises that consider both modern river discharge versus centennial accumulation rates and post lgm terrestrial production versus offshore isopachs mass balances indicate that about half of the total sediment production from the waipaoa escapes the study area moreover a coupled sediment transport hydrodynamic model and observations of textural trends on the shelf indicate that a large fraction of the sediment is carried outside the study area along the shelf to the northeast by the river plume or by combined current wave activity therefore we conclude that the wss is an open system with sediment escape from the present day through the lgm the organic matter associated with sediment as it moves from upland source to marine sink is a product of particle history and provides a record of materials that have cycled over timescales of days to millions of years the ubiquity of fossil organic carbon oc in both the terrestrial and marine realms of the waipaoa attests both to the chronic nature of its source crumbling mudstones further destabilized by land use and its biogeochemical recalcitrance modern oc persists by virtue of its continual production along the s2s transit and is buried and preserved within the adjacent marine depocenters the waipaoa contrasts with dispersal systems on wide energetic shelves e g the amazon and fly rivers where sediment is extensively refluxed in oxygenated overlying water resulting in the biogeochemical incineration of particulate oc the waipaoa like other small mountainous rivers on active margins exhibits a high riverine oc preservation efficiency 50 in its marine depocenters because of the relatively rapid event driven accumulation of sediment

el nino southern oscillation signal associated with middle holocene climate change in intercorrelated terrestrial and marine sediment cores north island new zealand a synchronous textural variation in intercorrelated high resolution sediment records from floodplain continental shelf and continental slope settings of the eastern north island new zealand provides evidence of increased storminess after ca 4 ka an upcore change in sediment texture reflects the transition to landsliding which supplanted fluvial incision as the dominant mode of sediment production in the middle holocene this signal which appears in all three records indicates a regional response to external forcing and records the impact of an intensified atmospheric circulation marking the establishment of the contemporary climate that is strongly influenced by the el nino southern oscillation the change in climate was a hemispheric event and in the southern hemisphere its timing is confirmed by independent proxy records from elsewhere in new zealand and the circum south pacific region

slip slidin away a post glacial environmental history of the waipaoa river basin abstract the dramatic changes that occurred to the post glacial landscape in the headwaters of the waipaoa river basin are a consequence of perturbations about the equilibrium that exists between the rate of tectonic uplift and fluvial incision at times when the amount of coarse sediment delivered to channels exceeds the capacity of streams to remove it the channel bed rises at the rate of tectonic uplift once bedload overcapacity is replaced by undercapacity and the alluvial cover is depleted streams reestablish contact with bedrock and recuperate the time lost to fluvial incision the first major perturbation occurred during the final phase of the last glaciation ca 33 17 5 cal ka when aggradation was driven by a climate forced variation in the relative supplies of sediment and water we suggest that the subsequent transformation of channels in the headwaters of the waipaoa river basin from alluvial to bedrock occurred as the atmospheric and oceanic circulation converged on their contemporary patterns ca 12 cal ka a second major perturbation that continues to the present began ca 1910 1912 ce when a massive increase in sediment load was accompanied by a modest increase in water discharge after the native vegetation cover in the headwaters was replaced by pasture the processes of terrace creation and incision are inherently unsteady and in five interim cases incision was arrested by a transient increase in the thickness of the alluvial cover that was a response to climatic forcing events that disrupted the native vegetation cover in the headwaters also modulated patterns of sediment dispersal and accumulation in other parts of the fluvial system and caused rapid storm driven infilling of the poverty bay flats tectonic subsidence dictates the course of the waipaoa river across poverty bay flats which because the modern rate of floodplain construction by vertical accretion is rapid relative to the amount of destruction by lateral channel migration has remained virtually unchanged for the past 100 years during this time the channel assumed a narrower deeper form that is in equilibrium with the contemporary supply of sediment and hydraulic regime

the role of vegetation on gully erosion stabilization at a severely degraded landscape a case study from calhoun experimental critical zone observatory abstract gully erosion was evidence of land degradation in the southern piedmont site of the calhoun critical zone observatory cczo during the cotton farming era understanding of the underlying gully erosion processes is essential to develop gully erosion models that could be useful in assessing the effectiveness of remedial and soil erosion control measures such as gully backfilling revegetation and terracing development and validation of process based gully erosion models is difficult because observations of the formation and progression of gullies are limited in this study analytic formulations of the two dominant gullying processes namely plunge pool erosion and slab failure are utilized to simulate the gullying processes in the 4 km2 holcombe s branch watershed in order to calibrate parameters of the gully erosion model gully features e g depth and area extracted from a high resolution lidar map are used after the calibration the gully model is able to delineate the spatial extent of gullies whose statistics are in close agreement with the gullies extracted from the lidar dem several simulations with the calibrated model are explored to evaluate the effectiveness of various gully remedial measures such as backfilling and revegetation the results show that in the short term the reshaping of the topographical surface by backfilling and compacting gullies is effective in slowing down the growth of gullies e g backfilling decreased the spatial extent of gullies by 21 46 and decreased the average depth of gullies by up to 9 revegetation however is a more effective approach to stabilizing gullies that would otherwise expand if no gully remedial measures are implemented analyses of our simulations show that the gully stabilization effect of revegetation varies over a wide range i e leading to 23 69 reduction of the spatial extent of gullies and up to 45 reduction in the depth of gullies depending on the selection of plant species and management practices

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

seismic cycles along the aleutian arc analysis of seismicity from 1957 through 1991 we catalog and relocate aleutian arc seismicity between 1957 and 1991 two great earthquakes ruptured the same 250 km long portion of the central aleutian arc the 1957 aleutian islands earthquake and the 1986 andreanof islands earthquake because accurate estimates of the moment distribution of the 1957 earthquake are not available the spatial distribution of aftershocks for each of these events is compared and tested against models describing the modes of occurrence of great subduction zone earthquakes earthquake relocations are based on p wave arrival times published in the international seismological summary the bureau central international seismologique and the international seismological centre bulletins and include corrections for the near source velocity structure associated with the down going slab magnitude estimates are extracted from bulletins and prior to 1964 are estimated by us from microfilmed records our catalog is complete above magnitude 5 5 aftershocks associated with the 1957 and 1986 earthquakes appear to occur in different areas east of the main shock epicenters aftershock locations are anticorrelated west of the main shock epicenter aftershocks of the 1986 earthquake tended to concentrate along the updip edge of aftershock clusters associated with the 1957 earthquake if we assume aftershocks rim the distribution of seismic moment release associated with each event these observations imply that the moment distribution of the 1986 earthquake was different from that of the 1957 earthquake this suggests that we should use caution in identifying mechanically strong portions of a fault asperities by simply mapping the moment distribution of a single great earthquake a fundamental tenet of the asperity model that rupture always occurs on the strongest portions of the fault with weaker portions rupturing either aseismically or dynamically as a result of rupture on a strong fault patch may in the case of the central aleutian arc not be correct thus observing the moment distribution from a single great earthquake may tell us little about what the distribution of moment release will look like during the next earthquake

slope instability in nicaragua triggered by hurricane mitch distribution of shallow mass movements the heavy rains associated with hurricane mitch triggered off a number of slope instability processes in several central american countries different instability processes have been acknowledged for the various mountainous regions of nicaragua an enormous movement of the casita volcano slopes resulted in numerous deaths and some deep movements have been reactivated on the other hand numerous shallow mass movements and debris flows have given rise to great material loss throughout a large part of nicaraguan mountains

the aleutian earthquake of june 10 1996 mw 7 9 ruptured parts of both the andreanof and delarof segments the epicenter of the aleutian earthquake of june 10 1996 is located in the delarof segment where a large subduction earthquake is expected however the aftershock area of the earthquake is not only in the delarof segment but also in the andreanof segment where the 1986 andreanof earthquake occurred previously we estimate the fault parameters of the 1996 earthquake by numerically computing the tsunami and comparing the waveforms with that recorded at adak the fault width is 30 km or less and the average slip is about 4 m the observed far field tsunamis around the pacific are also explained by the synthetic tsunami computed using the above fault parameters the results indicate that the 1996 earthquake ruptured parts of both the delarof and andreanof segments however the 1996 earthquake did not rupture the region of the largest moment release by the 1986 earthquake

quantifying temporal variations in landslide driven sediment production by reconstructing paleolandscapes using tephrochronology and lidar waipaoa river new zealand hillslope response to climate driven fluvial incision controls sediment export and relief generation in most mountainous settings following the shift to a warmer wetter climate after the last glacial maximum lgm 18 ka the waipaoa river new zealand rapidly incised up to 120 meters leaving perched low relief hillslopes unadjusted to that base level fall in the mangataikapua a 16 5 km2 tributary principally composed of weak melange pervasive post lgm landslides responded to 50 m of fluvial incision by sculpting and denuding 99 of the catchment by reconstructing lgm and younger paleosurfaces from tephra identified by electron microprobe analysis empa and lidar derived surface roughness we estimate the volume timing and distribution of hillslope destabilization in the mangataikapua and the relative contribution of landslide prone terrain to post lgm landscape evolution we calculate volume change between four paleosurfaces constrained by tephra age rerewhakaaitu 17 5 ka rotoma 9 4 ka whakatane 5 5 ka and waimihia 3 4 ka from the paleosurface reconstructions we calculate the total post lgm hillslope sediment contribution from the mangataikapua catchment to be 0 5 0 06 s d km3 which equates to a subcatchment averaged erosion rate of 1 6 mm yr 1 this is double the previous hillslope volume when normalized by study area demonstrating that landslide prone catchments disproportionately contribute to the terrestrial post lgm sediment budget finally we observe particularly rapid post waimihia erosion rates likely impacted by human settlement

tectonics of the zagros orogenic belt of iran new data and interpretations abstract the zagros orogenic belt of iran is the result of the opening and closure of the neo tethys oceanic realm and consists from northeast to southwest of three parallel tectonic subdivisions 1 1 the urumieh dokhtar magmatic assemblage 2 2 the sanandaj sirjan zone and 3 3 the zagros simply folded belt recent detailed and reconnaissance mapping and stratigraphie structural analyses in various parts of the belt indicate that the tectonics of the sanandaj sirjan zone is dominated by either large scale composite duplex structures or low and high angle ne dipping imbricate systems these thrust systems have transported numerous horses and sheets nappes of metamorphosed and non metamorphosed phanerozoic rocks for tens or possibly hundreds of kilometers stratigraphic evidence and synorogenic conglomerates indicate that thrusting was initiated in the late cretaceous and has continued episodically since that time shear sense indicators in various parts of the zone reveal a ne sw direction of transport thrust systems generated in each episode are superimposed upon the previous structures cutting across and displacing them and producing complicated stacks of thrust sheets southwestward transport and stacking of the thrust sheets has resulted in an increase of about 10 15 km in the thickness of the continental crust in the southwestern part of this zone the so called z main zagros thrust which has been traditionally considered as the boundary between the sanandaj sirjan zone and the zagros simply folded belt is by no means a single high angle reverse fault nor is it a narrow zone of crushed rocks but a series of low angle thrusts locally cut by normal faults these thrusts are indistinguishable from those mapped in the sanandaj sirjan zone and are geometrically part of the sanandaj sirjan zone structures there is no single thrust among them that can be singled out and referred to as the main one the boundary of the sanandaj sirjan zone with the urumieh dokhtar magmatic assemblage to the northeast is characterized by a series of structural depressions formed by compression rock sequences including ophiolite complexes exposed along this boundary are strongly dismembered sheared and mylonitized shearing planes and foliations are either subvertical or dipping at high angles to the northeast this zone is suggested to be the suture between the afro arabian and the iranian plates overall the intensity of deformation increases northeastward from the persian gulf mesopotamian basin where strata are undeformed and horizontal through the zagros simply folded belt which is characterized by en echelon doubly plunging flexural slip folds gentle to open in the southwest and close to locally sw overturned in the northeast the intensity of deformation continues to increase further northeastward through the sanandaj sirjan zone where thrust faulting is dominant this pattern suggests that the deformational front has migrated through time from the northeastern part of the sanandaj sirjan zone i e the suture zone to its present position in the central portion of the persian gulf mesopotamian foreland basin

long term modelling of landslides for different forest management practices long term effects of different forest management practices on landslide initiation and volume were analysed using a physically based slope stability model the watershed based model calculates the effects of multiple harvesting entries on slope stability by accounting for the cumulative impacts of a prior vegetation removal on a more recent removal related to vegetation root strength and tree surcharge four sequential clearcuts and partial cuts with variable rotation lengths were simulated with or without leave areas and with or without understorey vegetation in a subwatershed of carnation creek vancouver island british columbia the combined in nite slope and distributed hydrologic models used to calculate safety factor revealed that most of the simulated landslides were clustered within a 5 to 17 year period after initial harvesting in cases where suf cient time c 50 years lapsed prior to the next harvesting cycle partial cutting produced fewer landslides and reduced landslide volume by 1 4 to 1 6 fold compared to clearcutting approximately the same total landslide volume was produced when 100 per cent of the site was initially clearcut compared to harvesting 20 per cent of the area in successive 10 year intervals a similar nding was obtained for partial cutting vegetation leave areas were effective in reducing landsliding by 2 to 3 fold retaining vigorous understorey vegetation also reduced landslide volume by 3 8 to 4 8 fold the combined management strategies of partial cutting increasing rotation length provision of leave areas and retention of viable understorey vegetation offer the best alternative for minimizing landslide occurrence in managed forests copyright 2003 john wiley sons ltd

sediment budget to assess the geomorphic effect of a cyclonic storm new zealand abstract a short term sediment budget was constructed to assess the erosion response of a soft rock hill country watershed to an intense rainstorm event the watershed is located in a landslide prone area on the east coast of the north island new zealand during march 1988 753 mm of rain was recorded over a four day period with 320 mm and 329 mm on successive days known as cyclone bola this was the largest rainstorm event in the tutira watershed in the 93 year rainfall record the budget quantifies the total sediment generated during the storm the relative contribution of erosion processes involved the amount of sediment held in storage and the amount discharged into two lakes within the watershed a landform map of the watershed was constructed and the contribution of each landform type to the total budget was calculated a total of 1 35 0 13 million m3 of sediment was generated during the storm at an average of 420 m3 ha this is equivalent to a denudation value of 42 mm for the total watershed 3208 ha and 83 mm for the landforms severely affected by landsliding 1427 ha of the sediment generated 21 remained on hillslopes 22 was deposited on valley floors 51 was deposited on the lakebeds and the remaining 6 was discharged from the watershed via the lake outlet most of the sediment generated during the storm was from primary source areas on hill slopes with sediment in secondary storage providing only a small contribution landslide erosion was the main process accounting for 89 of the sediment generated channel tunnel gully and sheet erosion were only minor contributors to the budget six hillslope landforms which occupy only 44 of the watershed generated 90 of the sediment the results of this sediment budget when put in context with the storm magnitude frequency history being analysed from lake cores contribute to the identification of sustainable land use and management of soft rock hill country

application of the shetran basin scale landslide sediment yield model to the llobregat basin spanish pyrenees the first application of the shetran basin scale landslide erosion and sediment yield model is carried out for a major landsliding event in the upper 505 km2 of the llobregat basin in the eastern spanish pyrenees in november 1982 the model simulates the spatial distribution of shallow landslides and their sediment yield acknowledging uncertainty in the model parameter evaluation the aim of the application was not to reproduce the observed occurrence of landslides as accurately as possible with one simulation but to bracket the observed pattern with several simulations representing uncertainty in the key input conditions bounds on the landslide simulations were thus determined as a function of uncertainty in the vegetation root cohesion used in the model factor of safety calculations the resulting upper bound considerably overestimates the observed pattern 17 000 landslides compared with an observation of around 700 but it reproduces several of the principal clusters in the observed pattern the lower bound contains around 500 landslides the sediment yield estimates 2670 14 630 t km 2 are comparable to measurements elsewhere in the pyrenees for extreme events the results demonstrate an ability to simulate the basin scale landslide response to a rainfall event and the resulting sediment yield they also highlight the need for further research in setting the uncertainty bounds and in avoiding large overestimates of landslide occurrence arising in part from a current inability to model small scale controls for a basin of the given size copyright 2006 john wiley sons ltd

mineral chemistry of hydrothermal biotite from the kahang porphyry copper deposit ne isfahan central province of iran abstract the kahang porphyry cu deposit located northeast of isfahan city in central of iran is associated with a composite miocene stock and ranges in composition from diorite through granodiorite to quartz monzonite field observations and petrographic studies show that the emplacement of the kahang stock occurred in several pulses each associated with its related hydrothermal activity early hydrothermal alteration started with a potassic style in the central part of the system and produced a secondary biotite k feldspar magnetite assemblage accompanied by chalcopyrite and pyrite mineralization propylitic alteration that took place at the same time as the potassic alteration occurred in the peripheral portions of the stock subsequent phyllic alteration overprinted earlier potassic and propylitic alterations biotite grains from the potassic and phyllic zones show distinct chemical compositions the feo tio2 mno k2o and na2o concentrations in biotite from the phyllic alteration zone are lower than those from the potassic alteration zone the f and cl contents of biotite from the potassic alteration zone display relatively high positive correlation with the xmg the fluorine intercept values iv f from the potassic and phyllic alteration zones are strongly correlated with the fluorine chlorine intercept values iv f cl biotite geothermometry for the potassic and phyllic alteration zones based on the biotite geothermometer of beane 1974 yields a temperature range of 422 to 437 c mean 430 c and 329 to 336 c mean 333 c respectively the position of data in log xf xoh ratio vs xmg and xfe diagram suggests that biotite formed under dissimilar composition and temperature conditions in the potassic and phyllic alteration zones calculated log fugacity ratios of fh2o fhf fh2o fhcl and fhf fhcl show that hydrothermal fluids associated with the potassic alteration were distinctively different from those fluids associated with the phyllic alteration zone at kahang porphyry cu deposit the results of this research indicate that the chemistry of biotite is related to the chemical composition of the magma and the prevailing physical conditions during crystallization

a novel algorithm for designing the layout of additional boreholes abstract in an exploration project the placement of additional boreholes is based on the available information and engineering judgment which may result in a lack of information or redundant information in decision making this paper presents the use of dynamic multistage sampling to design directional and vertical boreholes to scan the subsurface for this purpose the potential collars of boreholes are determined within the survey area while the imaginary boreholes in the form of cone sides cover the area s lateral surface area and the concentric cones around the collars change with azimuth and dip angles the objective function is a criterion used to determine the optimal borehole s and update the input borehole database in each stage this iterative process continues until a stopping condition is satisfied the presented algorithm was executed and validated on both synthetic and field data from the eastern kahang region in iran in the synthetic case five additional boreholes were designated based on high grade and estimation error objectives that intersect two parts of the ore body ten proposed additional boreholes in the northeast region of kahang coincided with the high grade copper mineralization zone

comparison of satellite and air photo based landslide susceptibility maps landslide susceptibility maps can be prepared in a variety of ways many geoscientists favour the use of an overlay model approach in which several map layers are combined by some arithmetic rules to determine the potential for sliding in an area or region the resulting susceptibility maps although based on a subjective weighting of relevant factors can often be of high accuracy and utility in order to obtain the relevant input data for this type of analysis remotely sensed data are often used to date susceptibility mapping just as the mapping of historic and individual landslides has tended to require higher resolution imagery this has somewhat limited the application of landslide susceptibility mapping while high resolution air photo or satellite imagery is superior to lower resolution imagery for the purpose of mapping of historic and individual landslides such higher levels of resolution may not be required for the development of landslide susceptibility maps in order to determine if medium resolution satellite imagery such as spot or aster could provide the needed data for landslide susceptibility mapping a comparison was undertaken of landslide susceptibility model output resulting from the use of stereo napp aerial photography versus the use of data obtained from stereo spot imagery the test area selected for this study consisted of two watersheds pena canyon and big rock canyon situated west of santa monica california usa along the pacific coast highway both watersheds have a long and well documented history of landslide activity and sufficient geologic variability and complexity to provide a good test site the specific overlay model used in this evaluation required input data consistent with the needs of many other models of this type the model output derived from the two different data sources and presented here in the form of susceptibility maps were virtually identical statistical and difference analysis confirmed that both methods of obtaining input data provide similar results and successfully identified landslide prone areas these results suggest that satellite imagery in this instance spot images could potentially be used in lieu of conventional air photos to evaluate landslide susceptibility in many situations especially in the case of remote locations and or developing countries this capability should result in substantial savings in terms of time financial resources and overall viability

circum pacific seismic potential 1989 1999 the seismic potential for 96 segments of simple plate boundaries around the circum pacific region is presented in terms of the conditional probability for the occurrence of either large or great interplate earthquakes during the next 5 10 and 20 years i e 1989 1994 1989 1999 and 1989 2009 this study represents the first probabilistic summary of seismic potential on this scale and involves the comparison of plate boundary segments that exhibit varying recurrence times magnitudes and tectonic regimes presenting these data in a probabilistic framework provides a basis for the uniform comparison of seismic hazard between these differing fault segments as well as accounting for individual variations in recurrence time along a specific fault segment and uncertainties in the determination of the average recurrence time

seismicity trends and potential for large earthquakes in the alaska aleutian region the high likelihood of a gap filling thrust earthquake in the alaska subduction zone within this decade is indicated by two independent methods analysis of historic earthquake recurrence data and time to failure analysis applied to recent decades of instrumental data recent may 1993 earthquake activity in the shumagin islands gap is consistent with previous projections of increases in seismic release indicating that this segment along with the alaska peninsula segment is approaching failure based on this pattern of accelerating seismic release we project the occurrence of one or morem 7 3 earthquakes in the shumagin alaska peninsula region during 1994 1996 different segments of the alaska aleutian seismic zone behave differently in the decade or two preceding great earthquakes some showing acceleration of seismic release type a zones while others show deceleration type d zones the largest alaska aleutian earthquakes in 1957 1964 and 1965 originated in zones that exhibit type d behavior type a zones currently showing accelerating release are the shumagin alaska peninsula delarof and kommandorski segments time to failure analysis suggests that the large earthquakes could occur in these latter zones within the next few years

geomorphic change implied by regolith slope relationships on steepland hillslopes taranaki new zealand abstract slope angle and regolith depth were measured along profile lines covering a range of hillslopes in several small neighbouring drainage basins in taranaki hill country new zealand slope measurements show a cyclic variation along the length of broadly rectilinear profiles variation in slope on the lower portion of profiles adjacent to stream channels indicates that hillslopes have undergone phases of accelerated downcutting and hillslope rejuvenation a recent phase of increased erosion and hillslope rejuvenation is suggested for hillslopes steeper than 31 by the steep lowerslope and incised stream channel hillslope evolution occurs primarily by parallel retreat of steeper swale sites and slope decline during pauses in the rate of downcutting all slope profiles show a large range in regolith depth mean regolith depth of swale sites is highly correlated with mean profile slope angle mean regolith depth decreases and the frequency of landslides increase with increasing mean profile slope angle microtopographic variation in regolith depth is attributed mainly to vegetation effects recurrent landsliding and in part to bedrock curvature hillslope position and slope angle shallowing of regolith is caused by recurrent landsliding on steep swale sites fluvial erosion at the base of steep profiles and surface erosion on extremely convex spur sites the very shallow soil on the steep lowerslope portion of profiles suggests a phase of soil removal consistent with hillslope rejuvenation average depth of regolith is least at 97 cm and variability greatest on hillslopes with a profile mean exceeding 31 erosion rates are greater on these sites where soil is derived predominantly from underlying tertiary sandstone this is attributed to a greater frequency of landsliding compared to hillslopes with a profile slope less than 31 where a more regular and deeper average regolith of 153 cm infers a longer period of hillslope stability consistent with the high volcanic ash content of soils airfall andesitic volcanic ash deposited throughout the holocene has largely been removed from steeper sites the work demonstrates the need to interpret the frequency and distribution of landslides in context with natural geomorphic changes in order to assess the effect that landuse changes has on erosion rates

recycling of orogenic arc crust triggers porphyry cu mineralization in kerman cenozoic arc rocks southeastern iran pre collisional eocene oligocene arc diorites quartzdiorites granodiorites and volcanic equivalents in the kerman arc segment in central iran lack porphyry cu mineralization and ore deposits whereas collisional middle late miocene adakite like porphyritic granodiorites without volcanic equivalents host some of the world s largest cu ore deposits petrological and structural constraints suggest a direct link between orogenic arc crust evolution and the presence of a fertile metallogenic environment ore hosting kuh panj porphyry intrusions exhibit high sr 400 ppm low y 20 no negative eu anomalies eu eu 1 and relatively non radiogenic sr isotope signatures 87sr 86sr 0 7042 0 7047 relative to eocene oligocene granitoids mainly sr 12 la yb 15 eu eu 1 87sr 86sr 0 7053 0 7068 trace element modeling indicates peridotite melting for the barren eocene oligocene intrusions and a hydrous garnet bearing amphibolite source for middle late miocene ore hosting intrusions the presence of garnet implies collisional arc crustal thickening by shortening and basaltic underplating from about 30 35 to 40 45 km or 12 kbar the changes in residual mineralogy in the source of eocene to miocene rocks in the kerman arc segment reflect probing of a thickening arc crust by recycling melting of the arc crustal keel underplating of cu and sulfur rich melts from fertile peridotite generated a fertile metallogenic reservoir at or near the crust mantle boundary and dehydration melting under oxidizing conditions produced syn and post collisional ore hosting intrusions while the lack of post collisional volcanism prevented the venting of volatiles to the atmosphere from sulfur rich and oxidized adakitic magmas

reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics in river corridors a review of complementary approaches abstract until recently one way relationships between flow dynamics geomorphology and plant ecology were considered dominantly when studying the functioning of river systems whereby fluvial landforms and hydrogeomorphic processes drive the evolution of riparian plant communities however biological communities may significantly control geomorphic processes and have strong impacts on landform dynamics in order to fully identify the processes linked to river dynamics changes in time and space of fluvial landforms and associated plant communities conceptual multidisciplinary progress is clearly needed to understand the mutual interactions and feedbacks between fluvial landforms and vegetation community dynamics this paper presents a detailed literature review of fluvial geomorphology riparian plant ecology and hydraulic engineering knowledge the historical and recent development of ecological plant succession theory toward the integration of hydrogeomorphic disturbances is discussed as well as the integration of vegetation within geomorphology as a significant landform control factor incorporating both hydrogeomorphic controls on riparian vegetation dynamics and mechanical impacts of vegetation structures on flow properties and sediment dynamics recent progress in ecology hydraulic engineering and fluvial geomorphology emphasises interdependence between biological and physical forms and processes based on this literature review a fluvial biogeomorphic succession concept is proposed to link fluvial landform and riparian vegetation community evolution within a bi directional model the succession of fluvial landforms and associated vegetation communities is composed of four main critical phases that represent a shift in the relative dominance of hydrogeomorphic and ecological processes as a response to biostabilisation and passive bioconstruction processes the positive feedbacks associated with this shift lead to the development of characteristic biogeomorphic structures such as vegetated banks islands or floodplains which are moderated by the biogeomorphic functional roles of ecosystem engineers that induce or reinforce the positive feedbacks this fluvial biogeomorphic succession concept relates the natural darwinian selection and ecological succession theories to fluvial geomorphology

resistance to shallow landslide failure through root derived cohesion in east coast hill country soils north island new zealand measured shear strength cohesion and friction of airfall derived east coast hill country regolith is insufficient for the maintenance of existing regolith depth slope angle relationships in the catchment of lake waikopiro in northern hawke s bay new zealand if these regoliths are attributed with an additional increment of cohesion derived mechanically from a turf mat membrane existing depth slope angle distributions are explicable sites where failure has occurred have been measured and back analysis used to derive a range of values for additional mechanical cohesion values are in the range 0 2 7 6 kpa consistent with earlier findings this range is narrowed further to 0 7 6 9 kpa with assumptions regarding soil moisture status at failure copyright 1999 john wiley sons ltd

residual strength of clays in landslides folded strata and the laboratory the post peak drop in drained shear strength of an overconsolidated clay may be considered as taking place in two stages first at relatively small displacements the strength decreases to the fully softened or critical state value owing to an increase in water content dilatancy second after much larger displacements the strength falls to the residual value owing to reorientation of platy clay minerals parallel to the direction of shearing if the clay fraction is less than about 25 the second stage scarcely comes into operation the clay behaves much like a sand or silt with angles of residual shearing resistance typically greater than 20 degrees conversely when the clay fraction is about 50 residual strength is controlled almost entirely by sliding friction of the clay minerals and further increase in clay fraction has little effect the angles of residual shearing resistance of the three most commonly occurring clay minerals are approximately 15 degrees for kaolinite 10 degrees for illite or clay mica and 5 degrees for montmorillonite when the clay fraction lies between 25 and 50 there is a transitional type of behaviour residual strength being dependent on the percentage of clay particles as well as on their nature the post peak drop in strength of a normally consolidated clay is due only to particle reorientation measurements of strength on natural shear surfaces agree within practical limits of variation with values derived from back analysis of reactivated landslides this field residual strength can be recovered by multiple reversal shear box tests on cut plane samples but in high clay fraction materials it is typically somewhat higher than the strength measured in ring shear tests residual strength is little affected by variation in the slow rates of displacement encountered in reactivated landslides and in the usual laboratory tests but at rates faster than about 100 mm min qualitative changes take place in the pattern of behaviour a substantial gain in strength is followed with increasing displacement by a fall to a minimum value in clays and low clay fraction silts this minimum is not less than the slow or static residual but in clayey silts with clay fractions around 15 25 according to tests currently in progress the minimum can be as low as one half of the static value author trrl