Erosion Associated with Seismically-Induced Landslides in the Middle Longmen Shan Region, Eastern Tibetan Plateau, China

The 2008 Wenchuan earthquake and associated co-seismic landslide was the most recent expression of the rapid deformation and erosion occurring in the eastern Tibetan Plateau. The erosion associated with co-seismic landslides balances the long-term tectonic uplift in the topographic evolution of the region; however, the quantitative relationship between earthquakes, uplift, and erosion is still unknown. In order to quantitatively distinguish the seismically-induced erosion in the total erosion, here, we quantify the Wenchuan earthquake-induced erosion using the digital elevation model (DEM) differential method and previously-reported landslide volumes. Our results show that the seismically-induced erosion is comparable with the pre-earthquake short-term erosion. The seismically-induced erosion rate contributes ~50% of the total erosion rate, which suggests that the local topographic evolution of the middle Longmen Shan region may be closely related to tectonic events, such as the 2008 Wenchuan earthquake. We propose that seismically-induced erosion is a very important component of the total erosion, particularly in active orogenic regions. Our results demonstrate that the remote sensing technique of differential DEM provides a powerful tool for evaluating the volume of co-seismic landslides produced in intermountain regions by strong earthquakes.

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title: Seismically Induced Erosion and the Mass Balance of a Large Earthquake
abstract: Earthquakes create topographic relief by opposite displacements of the Earth's surface on either side of a fault. Over a seismic cycle most energy is released in large earthquakes, and they are thought to be the principal cause of relief formation in tectonically active areas. But the topographic effect of earthquakes is reduced by seismically induced erosion. Earthquakes trigger slope failure, often in proportion to their strength, and increase substrate erodibility through shattering of rock mass and coalescence of cracks. Intense mass wasting has been reported from the epicenters of many large earthquakes, and a link between earthquakes and increased fluvial sediment transport has been demonstrated. After an earthquake, enhanced erosion persists, and its intensity and decay determine the net topographic effect of the earthquake. We have calculated the mass balance and topographic effect of the MW7.6 Chi-Chi earthquake in west Taiwan. Rates of mass wasting in the Chi-Chi epicentral area increased fivefold due to the earthquake, and have decayed since then to background values. The sediment concentration in the epicentral Choshui River has closely tracked hillslope mass wasting, and from the excess sediment load of typhoon floods following the earthquake, we estimate that about half of the co- and post seismic surface elevation has been removed by seismically-induced erosion. Further erosion at background rates will annul the remaining earthquake topography faster than the return time of large earthquakes in this area. These findings have broad implications for the timing and magnitude of the erosional sediment flux from the Taiwan mountain belt and the mechanisms driving its orogenesis.

title: Mass wasting triggered by the 2008 Wenchuan earthquake is greater than orogenic growth
abstract: Shallow earthquakes lead to the uplift of mountain ranges, but also trigger landslides that remove mass. An analysis of the 2008 Wenshuan earthquake suggests that more material was removed from the orogen by widespread landslides than was added by coseismic uplift.

title: The role of landslides in mountain range evolution.
abstract: We review the role of landslides in current concepts of the topographic development of mountain ranges. We find that many studies in this field address basin- or orogen-scale competition between rock uplift and fluvial bedrock erosion. Hillslopes in general, and bedrock landslides in particular, are often assumed to respond rapidly to incision and development of the fluvial drainage network. This leads to a one-sided view of the geomorphic coupling between hillslopes and rivers that emphasizes the fluvial control of hillslopes, but ignores the alternative view that landslides can affect the fluvial network. There is growing evidence that landslides are a dominant source of sediment in mountain belts and that they exert a direct geomorphic control on fluvial processes. Landslides can influence the river network in a variety of ways, from determining basin area and drainage divide positions, to setting streamwise variations in sediment load and calibre. The geomorphic legacy of large landslides on hillslope and channel morphologies may persist for up to 104 yr, adding considerable variability to fluvial erosion and sedimentation patterns over these timescales. We identify a number of questions for future research and conclude that a better understanding and quantification of the geomorphic feedbacks between landslides and river channels builds an important link between short-term (  105 yr) landscape evolution models.

title: The importance of earthquake-induced landslides to long-term slope erosion and slope-failure hazards in seismically active regions
abstract: This paper describes a general method for determining the amount of earthquake-induced landsliding that occurs in a seismically active region over time; this determination can be used as a quantitative measure of the long-term hazard from seismically triggered landslides as well as a measure of the importance of this process to regional slope-erosion rates and landscape evolution. The method uses data from historical earthquakes to relate total volume of landslide material dislodged by an earthquake to the magnitude, M , and seismic moment, M0, of the earthquake. From worldwide data, a linear-regression relation between landslide volume, V, and M0 is determined as: V = M0/1018.9(± 0.13), where V is measured in m3 and M0 is in dyn-cm. To determine the amount of earthquake-generated landsliding over time, this relation is combined with data on seismic-moment release for a particular region, which may be derived from either earthquake-history or fault-slip data. The form of the M0−V relation allows the rate of production of earthquake-induced landslides over time to be determined from total rate of seismic-moment release without regard to the distribution of individual events, thus simplifying and generalizing the determination. Application of the method to twelve seismically active regions, with areas ranging from 13,275 to 2,308,000 km2, shows that erosion rates from earthquake-induced landslides vary significantly from region to region. Of the regions studied, the highest rates were determined for the island of Hawaii, New Zealand, western New Guinea, and the San Francisco Bay region of California. Significantly lower rates were determined for Iran, Tibet, the Sierra Nevada-Great Basin region of California, and central Japan (for the time period from 715 AD to the present). Intermediate rates were determined for Peru, southern California, onshore California, Turkey, and central Japan (for the time period from 1586 AD to the present). To determine the relative, long-term importance of seismically triggered landslides, these erosion rates are compared to erosion rates calculated for other slope processes and to rates calculated from fluvial sediment discharge. Comparisons with other slope processes indicate that earthquake-induced landslides are the predominant agents of slope erosion on the island of Hawaii, in the San Francisco Bay region, and in western New Guinea. For Hawaii, the San Francisco Bay region, and Sierra Nevada-Great Basin region of California, the erosion rates calculated for earthquake-induced landslides also exceed the regional erosion rates calculated from fluvial sediment discharge.

title: Landslides, earthquakes, and erosion
abstract: This paper relates landslide inventories to erosion rates and provides quantitative estimates of the landslide hazard associated with earthquakes. We do this by utilizing a three-parameter inverse-gamma distribution, which fits the frequency– area statistics of three substantially dcompleteT landslide-event inventories. A consequence of this general distribution is that a landslide-event magnitude mL=logNLT can be introduced, where NLT is the total number of landslides associated with the landslide event. Using this general distribution, landslide-event magnitudes mL can be obtained from incomplete landslide inventories, and the total area and volume of associated landslides, as well as the area and volume of the maximum landslides, can be directly related to the landslide-event magnitude. Using estimated recurrence intervals for three landslide events and the time span for two historical inventories, we estimate regional erosion rates associated with landslides as typically 0.1–2.5 mm year � 1 . We next give an empirical correlation between the earthquake magnitude, associated landslideevent magnitude, and the total volume of associated landslides. Using these correlations, we estimate that the minimum earthquake magnitudes that will generate landslides is M=4.3F0.4. Finally, using Gutenberg–Richter frequency-magnitude statistics for regional seismicity, we relate the intensity of seismicity in an area and the magnitude of the largest regional earthquakes to erosion rates. We find that typical seismically induced erosion rates in active subduction zones are 0.2–7 mm year � 1 and adjacent to plate boundary strike-slip fault zones are 0.01–0.7 mm year � 1 .

title: Regional patterns of earthquake‐triggered landslides and their relation to ground motion
abstract: We have documented patterns of landsliding associated with large earthquakes on three thrust faults: the Northridge earthquake in California, Chi-Chi earthquake in Taiwan, and two earthquakes on the Ramu-Markham fault bounding the Finisterre Mountains of Papua New Guinea. In each case, landslide densities are shown to be greatest in the area of strongest ground acceleration and to decay with distance from the epicenter. In California and Taiwan, the density of co-seismic landslides is linearly and highly correlated with both the vertical and horizontal components of measured peak ground acceleration. Based on this observation, we derive an expression for the spatial variation of landslide density analogous with regional seismic attenuation laws. In its general form, this expression applies to our three examples, and we determine best fit values for individual cases. Our findings open a window on the construction of shake maps from geomorphic observations for earthquakes in non-instrumented regions.

title: Landslide erosion controlled by hillslope material
abstract: Landslide erosion is a primary control of landscape relief. A wide-ranging analysis of landslide geometry shows that soil-based landslides are generally less voluminous than landslides that involve the failure of bedrock, and provides refined metrics for estimating the volume of a landslide from the area of the failure

title: Seismic mountain building: Landslides associated with the 2008 Wenchuan earthquake in the context of a generalized model for earthquake volume balance
abstract: Here we assess earthquake volume balance and the growth of mountains in the context of a new landslide inventory for the Mw7.9 Wenchuan earthquake in central China. Coseismic landslides were mapped from high-resolution remote imagery using an automated algorithm and manual delineation, which allows us to distinguish clustered landslides that can bias landslide volume calculations. Employing a power-law landslide area-volume relation, we find that the volume of landslide-associated mass wasting (~2.8+0.9/-0.7 km3) is lower than previously estimated (~5.7-15.2 km3) and comparable to the volume of rock uplift (~2.6±1.2 km3) during the Wenchuan earthquake. If fluvial evacuation removes landslide debris within the earthquake cycle, then the volume addition from coseismic uplift will be effectively offset by landslide erosion. If all earthquakes in the region followed this volume budget pattern, the efficient counteraction of coseismic rock uplift raises a fundamental question about how earthquakes build mountainous topography. To provide a framework for addressing this question, we explore a group of scaling relations to assess earthquake volume balance. We predict coseismic uplift volumes for thrust-fault earthquakes based on geophysical models for coseismic surface deformation and relations between fault rupture parameters and moment magnitude, Mw. By coupling this scaling relation with landslide volume-Mw scaling, we obtain an earthquake volume balance relation in terms of moment magnitude Mw, which is consistent with the revised Wenchuan landslide volumes and observations from the 1999 Chi-Chi earthquake in Taiwan. Incorporating the Gutenburg-Richter frequency-Mw relation, we use this volume balance to derive an analytical expression for crustal thickening from coseismic deformation based on an index of seismic intensity over a defined area. This model yields reasonable rates of crustal thickening from coseismic deformation (e.g.~0.1-0.5 km Ma-1 in tectonically active convergent settings), and implies that moderate magnitude earthquakes (Mw≈6-8) are likely responsible for most of the coseismic contribution to rock uplift, because of their smaller landslide-associated volume reduction. Our first-order model does not consider a range of factors (e.g., lithology, climate conditions, epicentral depth and tectonic setting), nor does it account for viscoelastic or isostatic responses to erosion, and there remain important uncertainties on the scaling relationships used to quantify coseismic deformation. Nevertheless, our study provides a conceptual framework and invites more rigorous modeling of seismic mountain building.

title: Did the 2008 Wenchuan Earthquake Lead to a Net Volume Loss
abstract: The topographic evolution of mountain landscapes is a coupling process of tectonic rock uplift, landslide erosion, and valley incision etc. A widely accepted notion is that an earthquake will build up the mountainous topography, whereas some researchers suggest that the 2008 Wenchuan earthquake tumbled down the mountain because the wasting mass volume due to landsliding is two to six times larger than the gain volume caused by rock uplift. The purpose of this paper is to compare the wasting mass volume due to seismic landsliding with the gain volume caused by rock uplift related to the 2008 Wenchuan event based on a new detailed landslide inventory prepared by visual interpretation of aerial photos and satellite images of high resolutions. The results show that about 5.9 km3 materials, generated by nearly 200,000 landslides triggered by the Wenchuan earthquake, are distributed in the landslide intensity area. Although the landslides volume is larger than the published volume of tectonic rock uplift (2.6 ± 1.2 km3), it is rather smaller than that from the previous study. We think it is not enough only to account for the co-seismic landslide volume and uplifted volume in the study of landscape evolution of the Longmenshan mountain area where the Wenchuan event took place. Orogenic evolution is affected by a variety of factors, such as co-seismic and interseismic crustal uplift, and isostatic compensation of mass removed from the surface of the earth which leads to orogenic growth, whereas co-seismic landslides and river erosion can destroy mountainous topography.

title: Optimized volume models of earthquake-triggered landslides
abstract: In this study, we proposed three optimized models for calculating the total volume of landslides triggered by the 2008 Wenchuan, China Mw 7.9 earthquake. First, we calculated the volume of each deposit of 1,415 landslides triggered by the quake based on pre- and post-quake DEMs in 20 m resolution. The samples were used to fit the conventional landslide “volume-area” power law relationship and the 3 optimized models we proposed, respectively. Two data fitting methods, i.e. log-transformed-based linear and original data-based nonlinear least square, were employed to the 4 models. Results show that original data-based nonlinear least square combining with an optimized model considering length, width, height, lithology, slope, peak ground acceleration, and slope aspect shows the best performance. This model was subsequently applied to the database of landslides triggered by the quake except for two largest ones with known volumes. It indicates that the total volume of the 196,007 landslides is about 1.2 × 1010 m3 in deposit materials and 1 × 1010 m3 in source areas, respectively. The result from the relationship of quake magnitude and entire landslide volume related to individual earthquake is much less than that from this study, which reminds us the necessity to update the power-law relationship.

title: Quantification of mass wasting volume associated with the giant landslide Daguangbao induced by the 2008 Wenchuan earthquake from persistent scatterer InSAR
abstract: The spaceborne interferometric synthetic aperture radar (InSAR) with persistent scatterer (PS) is utilized to retrieve the spatial characteristics of the largest coseismic landslide Daguangbao, induced by the Ms 8.0 Wenchuan earthquake in Sichuan Province, China. The available twenty interferometric pairs with good coherence selected from the ALOS/PALSAR imagery data covering the Longmen Shan mountainous area are used in the study. We have constructed a natural geodetic observation network with numerous scattered bare rocks emerging after the earthquake and coseismic landslide events, which are effectively recognized as the radar persistent scattering objects. The spatial connections between adjacent PS are established to form observation baselines with differential parameters related to topography and deformation, which are determined by the least squares method from time-series interferometric phase analysis. The post-seismic topographic change relative to the pre-seismic over the landslide area is spatially mapped from the PS network adjustment solution. The quantitative estimation of local elevation change, mass sliding volume and deposit thickness associated with the landslide is conducted. The spatial pattern of mass movement suggests that the giant landslide is characterized by a major sliding length of 4350 m along the NE–SW directions with an extension width of 3400 m along the Huangdongzi gully, and a peak height change of 535 m in the vertical direction. The affected area of landslide mass movement reaches 7.2 km2 with the volume up to 1.28 billion m3. The study also demonstrates the potential of persistent scatterer InSAR technique as an alternative to allow the quantitative measurement of mass wasting volume associated with earthquake-induced giant landslides.

title: Modeling Accumulated Volume of Landslides Using Remote Sensing and DTM Data
abstract: Landslides, like other natural hazards, such as avalanches, floods, and debris flows, may result in a lot of property damage and human casualties. The volume of landslide deposits is a key parameter for landslide studies and disaster relief. Using remote sensing and digital terrain model (DTM) data, this paper analyzes errors that can occur in calculating landslide volumes using conventional models. To improve existing models, the mechanisms and laws governing the material deposited by landslides are studied and then the mass balance principle and mass balance line are defined. Based on these ideas, a novel and improved model (Mass Balance Model, MBM) is proposed. By using a parameter called the “height adaptor”, MBM translates the volume calculation into an automatic search for the mass balance line within the scope of the landslide. Due to the use of mass balance constraints and the height adaptor, MBM is much more effective and reliable. A test of MBM was carried out for the case of a typical landslide, triggered by the Wenchuan Earthquake of 12 May 2008.

title: Co-seismic thrusting rupture and slip distribution produced by the 2008 Mw 7.9 Wenchuan earthquake, China
abstract: Field investigations reveal that the Mw 7.9 Wenchuan (China) earthquake of 12 May 2008 produced a 285-km-long surface rupture zone, with dominantly thrusting slip accompanied by a right-lateral component along the central-northern segments of the zone, and left-lateral component along the southern segment, along the Longmen Shan Thrust Belt, eastern margin of the Tibetan Plateau. The co-seismic ruptures mainly occurred along the pre-existing Yingxiu–Beichuan, Guanxian–Anxian, and Qingchuan faults, which are the main faults of the Longmen Shan Thrust Belt. The displacements measured in the field are approximately 0.5–6.5 m in the vertical (typically 1–3 m), accompanied by an average left-lateral component of < 2 m along the 50-km-long southernmost segment of the rupture zone and an average right-lateral component of < 1 m along the 150-km-long central-northern segments. The maximum thrust slip amount is estimated to be ~ 10 m, accompanied by 9 m of shortening across the rupture zone; this finding is consistent with estimates based on seismic data. The rupture length and maximum vertical displacement are the largest among all intracontinental thrust-type earthquakes reported to date. Our findings demonstrate that i) the Wenchuan earthquake occurred upon pre-existing active faults of the Longmen Shan Thrust Belt, thereby controlling the spatial distribution of co-seismic surface rupture and displacement, and the rupture processes of the earthquake; ii) the long rupture length and large thrusting slip resulted from compressive stress associated with eastward extrusion of the Tibet Plateau as it accommodates the ongoing penetration of the Indian Plate into the Eurasian Plate; and iii) present-day shortening strain upon the eastern margin of the Tibetan Plateau is mostly released by seismic slip along thrust faults within the Longmen Shan Thrust Belt.

title: Co-seismic ruptures of the 12 May 2008, Ms 8.0 Wenchuan earthquake, Sichuan: East–west crustal shortening on oblique, parallel thrusts along the eastern edge of Tibet
abstract: The M s 8.0, Wenchuan earthquake, which devastated the mountainous western rim of the Sichuan basin in central China, produced a surface rupture over 200 km-long with oblique thrust/dextral slip and maximum scarp heights of ~ 10 m. It thus ranks as one of the world's largest continental mega-thrust events in the last 150 yrs. Field investigation shows clear surface breaks along two of the main branches of the NE-trending Longmen Shan thrust fault system. The principal rupture, on the NW-dipping Beichuan fault, displays nearly equal amounts of thrust and right-lateral slip. Basin-ward of this rupture, another continuous surface break is observed for over 70 km on the parallel, more shallowly NW-dipping Pengguan fault. Slip on this latter fault was pure thrusting, with a maximum scarp height of ~ 3.5 m. This is one of the very few reported instances of crustal-scale co-seismic slip partitioning on parallel thrusts. This out-of-sequence event, with distributed surface breaks on crustal mega-thrusts, highlights regional, ~ EW-directed, present day crustal shortening oblique to the Longmen Shan margin of Tibet. The long rupture and large offsets with strong horizontal shortening that characterize the Wenchuan earthquake herald a re-evaluation of tectonic models anticipating little or no active shortening of the upper crust along this edge of the plateau, and require a re-assessment of seismic hazard along potentially under-rated active faults across the densely populated western Sichuan basin and mountains.

title: Decoupling of erosion and precipitation in the Himalayas
abstract: The hypothesis that abrupt spatial gradients in erosion can cause high strain rates in active orogens has been supported by numerical models that couple erosional processes with lithospheric deformation via gravitational feedbacks1,2,3. Most such models invoke a ‘stream-power’ rule, in which either increased discharge or steeper channel slopes cause higher erosion rates. Spatial variations in precipitation and slopes are therefore predicted to correlate with gradients in both erosion rates and crustal strain. Here we combine observations from a meteorological network across the Greater Himalaya, Nepal, along with estimates of erosion rates at geologic timescales (greater than 100,000 yr) from low-temperature thermochronometry. Across a zone of about 20 km length spanning the Himalayan crest and encompassing a more than fivefold difference in monsoon precipitation, significant spatial variations in geologic erosion rates are not detectable. Decreased rainfall is not balanced by steeper channels. Instead, additional factors that influence river incision rates, such as channel width and sediment concentrations, must compensate for decreasing precipitation. Overall, spatially constant erosion is a response to uniform, upward tectonic transport of Greater Himalayan rock above a crustal ramp.

title: Erosional control on the dynamics of low-convergence rate continental plateau margins
abstract: S U M M A R Y Over the last decade, thermomechanical models have revealed the control of both tectonics and erosion on the morphology of continental plateaus margins. However, unravelling the specific effects of these two coupled processes has been difficult in practice. Here, to assess the control of erosion, we investigate the dynamics of the eastern and the northern borders of the Tibetan Plateau, which are characterized by a low convergence rate and a steep topographic escarpment adjacent to the Sichuan and Tarim basins, respectively. Thermomechanical modelling of continental lithosphere coupled with fluvial denudation reveals that important crustal deformation with large-scale horizontal displacements can occur, without any convergence, as a response to mass transfer due to gravitational collapse and to erosional unloading. These processes are sensitive to crustal structure, geothermal gradient as well as surface erosion. At a timescale of several million years, our results suggest that this denudation-triggered deformation exerts a primary control on the evolution of those plateau margins by counterbalancing the mass removal due to erosion and stabilizing the topographic escarpment. This finding supports a possible explanation for the morphology of the Longmen Shan, eastern Tibet, in which the paradoxical combination of persistent high-topographic gradients close to the foreland and low convergence rates can be related to the influence of erosion on deformation patterns.

title: Topographic controls on erosion rates in tectonically active mountain ranges
abstract: The functional relationship between erosion rate and topography is central to understanding both controls on global sediment flux and the potential for feedback between tectonics, climate, and erosion in shaping topography. Analysis of a high-resolution (10-m-grid) DEM transect across the convergent orogen of the Olympic Mountains reveals a non-linear relation between long-term erosion rates and mean slope, similar to a model for hillslope evolution by landsliding in steep terrain. The DEM data also reveal a relation between mean slope and mean local relief. Coarser-scale (1-km-grid) global analysis of the relation between erosion rate and mean local relief reveals different trends for areas with low erosion rates and tectonically active mountain ranges, with the composite relation being well-described by non-linear models. Together these analyses support the emerging view that erosion rates adjust to high rates of tectonically driven rock uplift primarily through changes in the frequency of landsliding rather than hillslope steepness, and imply that changes in local relief play a minor role in controlling landscape-scale erosion rates in tectonically active mountain ranges. - 2002 Elsevier Science B.V. All rights reserved.

title: Spatial distribution of denudation in Eastern Tibet and regressive erosion of plateau margins
abstract: article i nfo The Longmen Shan range is one of the major topographic and structural features of the eastern margin of the Tibetan Plateau. With an impressive topographic gradient and low convergence rates across the range this region has raised important questions concerning the dynamics of plateau margin settings, such as the long- term mechanisms of topographic evolution. The investigation of the distribution in space and time of denudation can provide critical insight into such dynamics and shed light on still unresolved controversies. For that purpose, we present a new dataset that documents the intensity and distribution of denudation processes across this plateau margin through field survey of fluvial incision markers, quantitative geomorphology and cosmogenic nuclide derived basin-wide erosion rates. Erosion is b0.5 mm/year in the frontal region of the Longmen Shan and between 0.5 and 1 mm/year further west, with a gradual decrease when reaching the northern headwaters of the Min Jiang watershed, adjacent to the beginning of the Tibetan Plateau. The spatial distribution of denudation inferred from the various methods we use suggests that most of the differential uplift in the Central Longmen Shan is accommodated by the Beichuan Fault and frontal structures located in the foothills. The denudation pattern seems also to reflect the large-scale propagation of erosion from the Sichuan Basin toward the Plateau. This suggests that the Longmen Shan range is submitted to the combined influences of slow thrusting activity on the frontal structures and progressive westward regressive erosion as a probable response to a pulse of uplift of the Tibetan Plateau Eastern margin, that

title: Tectonic geomorphology along the eastern margin of Tibet: insights into the pattern and processes of active deformation adjacent to the Sichuan Basin
abstract: We present a review and synthesis of the tectonic geomorphology along the eastern margin of the Tibetan Plateau adjacent to and north of the Sichuan Basin. Re-evaluation of spatial variations in the form of fluvial longitudinal profiles provides a refined image of the distribution of anomalously steep channels. Three new analyses demonstrate that these variations in channel steepness reflect variations in the locus and rate of differential rock uplift. First, measurements of channel width along trunk streams reveal systematic co-variations in channel hydraulic geometry and slope that suggests channels are dynamically adjusted to spatial variations in erosion rate. Second, recent determinations of the functional relationship between channel steepness indices and erosion rate allow a quantitative estimation of erosion rate from channel profile form. Third, comparison of rock uplift patterns to variations in the distribution of slip associated with the 2008 Wenchuan earthquake confirms that channel gradients reflect differential rock uplift. Our analysis suggests that reactivated fault systems adjacent to the Sichuan Basin are primarily responsible for accommodating differential rock uplift, but that rock uplift northward along the margin is not associated with active faults and is likely sustained by flow and thickening in the deep crust.

title: Focused modern denudation of the Longmen Shan margin, eastern Tibetan Plateau
abstract: We use river sediment load data to map the pattern of modern denudation across the Longmen Shan margin of the Tibetan Plateau. Suspended sediment load, with corrections of bed load and solute load contributions, is used to calculate watershed-averaged denudation rates. Decadal erosion is spatially heterogeneous, and seasonally modulated by monsoon flows, which account for 80–90% of the sediment load. Enhanced denudation occurs in a ∼50 km wide band on the hanging wall of the Longmen Shan and Huya fault zones, reaching 0.5–0.8 mm/yr. These rates are similar to kyr-scale rates deduced from cosmogenic 10Be and to Myr-scale rates from low-temperature thermochronology. The sediment flux-derived erosion rates decrease with increasing distance plateauward, to less than 0.05 mm/yr at a distance ∼200 km northwest of the foot of the Longmen Shan. The gradient in precipitation across this margin alone cannot explain the one order of magnitude spatial difference in erosion. Rather, the river sediment load data delineates a zone of relatively rapid denudation around active faults that carry the Longmen Shan in their hanging wall. From the similarity of denudation rates measured over Myr, kyr, and decadal time scales, we propose that erosion of the Longmen Shan margin has approached a flux steady state. The erosional efflux is balanced by advection of rock toward the Longmen margin above the ∼20°NW dipping ramp of the margin-bounding fault. Our results suggest that high amounts of landslide material mobilized by earthquakes such as the Mw 7.9 2008 Wenchuan event are gradually removed by rivers, smoothing sediment flux over time. Our results also suggest that caution should be exercised when interpreting young cooling ages as evidence of the initiation of plateau uplift. Advection of an already high plateau into the belt of higher erosion rate at the Longmen Shan could also give rise to an abrupt cooling history.

title: Co-seismic landslides induced by the 2008 Wenchuan magnitude 8.0 Earthquake, as revealed by ALOS PRISM and AVNIR2 imagery data
abstract: The magnitude 8.0 Wenchuan Earthquake occurred on 12 May 2008 in Sichuan Province, China, resulting in numerous landslides along the marginal zone between the Tibetan Plateau and Sichuan Basin. We used Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and Advanced Visible and Near Infrared Radiometer type 2 (AVNIR 2) data from the Advanced Land Observing Satellite (ALOS) and Landsat Enhanced Thematic Mapper (ETM) images acquired before and after the earthquake to identify co-seismic landslides. Interpretations of remote sensing images, combined with fieldwork, reveal that co-seismic landslides are mainly restricted to a corridor of <18 km in width about the co-seismic surface rupture zone along a length of >285 km along pre-existing active faults of the Longmenshan Thrust Belt. The landslides mainly occurred upon steep slopes (dips of 30–75°). The distribution and topographic features of co-seismic landslides indicate a close relationship with seismic slip along the co-seismic surface rupture zone. The locations of landslides are controlled by the tectonic topography developed along pre-existing active faults of the Longmenshan Thrust Belt. Our results demonstrate that remote sensing techniques provide a powerful tool for identifying co-seismic landslides produced in intermountain regions by strong earthquakes.

title: Topographic changes due to the 2008 Mw 7.9 Wenchuan earthquake as revealed by the differential DEM method
abstract: Landscape evolution in active orogenic regions is inevitably affected by the repeated strong earthquakes triggered by the corresponding active faults. However, the lack of adequate methods for the documentation and monitoring of mountain-building processes has resulted in a shortage of quantitative estimates of orogenic and eroded volumes. A strong earthquake and its associated co-seismic landslides represent a sudden pulse in landscape evolution in tectonically active areas. The 2008 Mw 7.9 Wenchuan earthquake dramatically modified the topography of the Longmen Shan region. Based on topographic data before the earthquake and stereo pairs of post-earthquake remote sensing imagery, we derived pre- and post-earthquake DEMs (digital elevation models) of the three regions along the Longmen Shan Thrust Belt. By comparing the geomorphic features before and after the earthquake, we find that the Wenchuan earthquake smoothed the steep relief and caused a co-seismic uplift of the Longmen Shan region. The medium-relief regions increased; however, the high-relief regions decreased, indicating that the local relief is controlled by repeated strong earthquakes. The changed slope aspect indicates that the formation and modification of the east- and west-facing slopes are controlled by tectonic events in the Longmen Shan region, which might be associated with the regional stress field. However, the unchanged aspects of other slopes might be controlled by long-term erosion rather than tectonic events. The topographic changes, landslide volume and co-seismic uplift indicate that the greatest seismically induced denudation occurred in association with a thrust faulting mechanism and low-angle fault geometry. Our findings reveal that the local relief has been shaped by the localized, seismically induced high rate of denudation within the plateau margins, and that the formation of local relief is also related to tectonic events, especially the events that have occurred on low-angle faults. This study also indicates that the multi-temporal DEM differential method is valuable in detecting seismically induced topographic change.

title: Morphogenic uncertainties of the 2008 Wenchuan Earthquake: Generating or reducing?
abstract: Landscape evolution in active orogen region is inevitably affected by landslides associated with strong earthquakes, rain or storm. However, quantitative studies of the orogenic or eroded volumes are rarely demonstrated. The 2008 Wenchuan Earthquake triggered serious landsliding, consequently, a large amount of landslide material. However, the landslide volume is estimated mainly on the landslides areas interpreted in their semi-automated landslide mapping algorithm. However, the total volume of landslides triggered by the Wenchuan Earthquake amounts to 5–10 times bigger than the expected upper bound according to the empirical correlation between “total landslide volume” and “moment magnitude”. Here we show that the total landslide volume estimation has large uncertainties to be used to determine whether the Wenchuan Earthquake generates or reduces relief. Thus, the widely held view that large dip-slip and oblique-slip earthquakes build mountainous topography may still be applicable to the Wenchuan Earthquake in Longmen Shan area. To challenge this view, simple landslide volume and co-seismic uplift comparison is not enough, i.e., more data are needed.

title: Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: Inferences from 40Ar/39Ar and (U‐Th)/He thermochronology
abstract: High topography in central Asia is perhaps the most fundamental expression of the Cenozoic Indo-Asian collision, yet an understanding of the timing and rates of development of the Tibetan Plateau remains elusive. Here we investigate the Cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the Sichuan Basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed. Temperature-time paths inferred from ^(40)Ar/^(39)Ar thermochronology of biotite, multiple diffusion domain modeling of alkali feldspar ^(40)Ar release spectra, and (U-Th)/He thermochronology of zircon and apatite imply that rocks at the present-day topographic front of the plateau underwent slow cooling ( 30°–50°C/m.y.) coincident with exhumation from inferred depths of ∼8–10 km, at denudation rates of 1–2 mm/yr. Samples from the interior of the plateau continued to cool relatively slowly during the same time period (∼3°C/m.y.), suggesting limited exhumation (1–2 km). However, these samples record a slight increase in cooling rate (from <1 to ∼3°C/m.y.) at some time during the middle Tertiary; the tectonic significance of this change remains uncertain. Regardless, late Cenozoic denudation in this region appears to have been markedly heterogeneous, with the highest rates of exhumation focused at the topographic front of the plateau margin. We infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable Sichuan Basin and thus marks the onset of deformation related to the development of the Tibetan Plateau in this region. The present margin of the plateau adjacent to and north of the Sichuan Basin is apparently no older than the late Miocene or early Pliocene (∼5–12 Ma).

title: Beyond threshold hillslopes: Channel adjustment to base-level fall in tectonically active mountain ranges
abstract: Numerous empirical and model-based studies argue that, in general, hillslopes and river channels increase their gradients to accommodate high rates of base-level fall. To date, however, few data sets show the dynamic range of both these relationships needed to test theoretical models of hillslope evolution and river incision. Here, we utilize concentrations of 10 Be in quartz extracted from river sand on the eastern margin of the Tibetan Plateau to explore relationships among short-term (10 2 –10 5 a) erosion rate, hillslope gradient, and channel steepness. Our data illustrate nonlinear behavior and a threshold in the relationship between erosion rate and mean hillslope gradient, confi rming the generalization that hillslopes around the world are limited by slope stability and cease to provide a metric for erosion at high rates (>~0.2 mm/a). The relationship between channel steepness index and erosion rate is also nonlinear, but channels continue to steepen beyond the point where threshold hillslopes emerge up to at least 0.6 mm/a, demonstrating that channel steepness is a more reliable topographic metric than mean hillslope gradient for erosion rate and that channels ultimately drive landscape adjustment to increasing rates of base-level fall in tectonically active settings.

title: Controls on fluvial evacuation of sediment from earthquake-triggered landslides
abstract: Large earthquakes in active mountain belts can trigger landslides, which mobilize large volumes of clastic sediment. Delivery of this material to river channels may result in aggradation and flooding, while sediment residing on hillslopes may increase the likelihood of subsequent landslides and debris flows. Despite recognition of these processes, the controls on the residence time of coseismic landslide sediment in river catchments remain poorly understood. Here we assess the residence time of fine-grained ( 5 mm day–1). Together with previous observations from the C.E. 1999 Chi-Chi earthquake in Taiwan, our results demonstrate the importance of landslide density and runoff intensity in setting the duration of earthquake-triggered landslide impacts on river systems.

title: Dilution of 10Be in detrital quartz by earthquake-induced landslides: Implications for determining denudation rates and potential to provide insights into landslide sediment dynamics
abstract: The concentration of 10Be in detrital quartz (10Beqtz) from river sediments is now widely used to quantify catchment-wide denudation rates but may also be sensitive to inputs from bedrock landslides that deliver sediment with low 10Beqtz. Major landslide-triggering events can provide large amounts of low-concentration material to rivers in mountain catchments, but changes in river sediment 10Beqtz due to such events have not yet been measured directly. Here we examine the impact of widespread landslides triggered by the 2008 Wenchuan earthquake on 10Beqtz in sediment samples from the Min Jiang river basin, in Sichuan, China. Landslide deposit material associated with the Wenchuan earthquake has consistently lower 10Beqtz than in river sediment prior to the earthquake. River sediment 10Beqtz decreased significantly following the earthquake downstream of areas of high coseismic landslide occurrence (i.e., with greater than ∼0.3% of the upstream catchment area affected by landslides), because of input of the 10Be-depleted landslide material, but showed no systematic changes where landslide occurrence was low. Changes in river sediment 10Beqtz concentration were largest in small first-order catchments but were still significant in large river basins with areas of 104–105 km2104–105 km2. Spatial and temporal variability in river sediment 10Beqtz has important implications for inferring representative denudation rates in tectonically active, landslide-dominated environments, even in large basins. Although the dilution of 10Beqtz in river sediment by landslide inputs may complicate interpretation of denudation rates, it also may provide a possible opportunity to track the transport of landslide sediment. The associated uncertainties are large, but in the Wenchuan case, calculations based on 10Be mixing proportions suggest that river sediment fluxes in the 2–3 years following the earthquake increased by a similar order of magnitude in the 0.25–1 mm and the <0.25 mm size fractions, as determined from 10Beqtz mixing calculations and hydrological gauging, respectively. Such information could provide new insight into sediment transfer, with implications for secondary sediment-related hazards and for understanding the removal of mass from mountains.

title: Tectonics of the Longmen Shan and Adjacent Regions, Central China
abstract: The Longmen Shan region includes, from west to east, the northeastern part of the Tibetan Plateau, the Sichuan Basin, and the eastern part of the eastern Sichuan fold-and-thrust belt. In the northeast, it merges with the Micang Shan, a part of the Qinling Mountains. The Longmen Shan region can be divided into two major tectonic elements: (1) an autochthon/parautochthon, which underlies the easternmost part of the Tibetan Plateau, the Sichuan Basin, and the eastern Sichuan fold-and-thrust belt; and (2) a complex allochthon, which underlies the eastern part of the Tibetan Plateau. The allochthon was emplaced toward the southeast during Late Triassic time, and it and the western part of the autochthon/parautochthon were modified by Cenozoic deformation. The autochthon/parautochthon was formed from the western part of the Yangtze platform and consists of a Proterozoic basement covered by a thin, incomplete succession of Late Proterozoic to Middle Triassic shallow-marine and nonmarine sedimentary rocks interru...

title: Emplacement of the Longmen Shan Thrust-Nappe Belt along the eastern margin of the Tibetan Plateau
abstract: The topographic descent from the eastern margin of the Tibetan Plateau to the Sichuan Basin passes through the Longmen Shan Thrust—Nappe Belt, which is sub-divided by six NW-dipping, major listric thrusts, with accompanying duplexes and imbricate fans, into five large-scale nappes. Each nappe has its own stratigraphic and deformational features. In the inner Longmen Shan (Longmen Mountains), allochthonous nappe units have incorporated both Mesoproterozoic basement and Sinian (Neoproterozoic) to Triassic cover sequences as ‘thick-skinned’ horses; whereas in the frontal Longmen Shan, Sinian—Cretaceous cover sediments have been stripped from the basement as ‘thin-skinned’ fold and thrust sheets, including the extensively distributed klippen structures. Pre-thrusting extension during Devonian to middle late Triassic times resulted in syn-depositional normal faults. Structural inversion of these faults initiated the ‘Peng Xian-Guan Xian Basement Complex’, Jiuding Shan and Tangwangzhai nappes during the early episode of the Indosinian orogeny (Norian to Rhaetian). This was followed by episodic thrusting during latest Triassic to Early Cretaceous times to develop the Guan Xian-An Xian and Southeastern Marginal nappes that have incorporated sediments from the neighbouring foreland basin into the frontal part of the Thrust—Nappe Belt. During a late Miocene reactivation of the pre-existing thrusts. differential thrusting occurred across the Thrust—Nappe Belt.

title: Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the Tibetan Plateau
abstract: (2007), Active tectonics of the Beichuan and Pengguan faults at the eastern margin of the TibetanPlateau, Tectonics, 26, TC4005, 10.1029/2006TC001987. To view the published open abstract, go tohttp://dx.doi.org and enter the DOIUse policy

title: Longmen Shan fold-thrust belt and its relation to the western Sichuan Basin in central China: New insights from hydrocarbon exploration
abstract: The Longmen Shan fold-thrust belt is one of the key regions of demonstrable Mesozoic–Cenozoic tectonic evolution in China, and the Sichuan Basin was the first natural-gas-producing area in China. In this article, the structural features of the Longmen Shan belt are presented, using both seismic profiles and field data. The complex structures of the northeast-trending Longmen Shan fold-thrust belt and its foreland in the western Sichuan Basin are formed by southeast-directed thrusting. Several eastward-verging, rootless thrust sheets and imbricates of Cambrian–Triassic rocks have been recognized in the northern Longmen Shan belt. Evidence suggests that the northern Longmen Shan belt experienced at least two major periods of deformation in the Late Triassic and Cenozoic. However, the southern Longmen Shan belt is represented by the basement-involved thrust structures and klippen, and its major periods of deformation were in the latest Cretaceous–early Cenozoic. Sedimentary features in the western Sichuan Basin reflect a two-phase flexural-loading history and illustrate that the Late Triassic foreland basin extends along the foredeep of the entire length of the Longmen Shan belt, but the uppermost Cretaceous–Paleogene rejuvenated foreland basin is restricted in the southern part of the western Sichuan Basin. Structural geometries suggest that prospective traps are mainly developed in the frontal zone of the Longmen Shan fold-thrust belt and in the southern part of the western Sichuan Basin. One of the major contributions of this article is finding preexisting Paleozoic rift basins under the Cenozoic thin-skinned thrust belts, which represent a new potential hydrocarbon play.

title: Topography reveals seismic hazard
abstract: The devastating earthquake in the Chinese province of Sichuan struck an area that was not expected to suffer seismic activity of such magnitude. Yet topographic analyses of the region indicate active deformation, suggesting a way of refining maps of earthquake risk elsewhere.

title: Rock avalanches triggered by oblique-thrusting during the 12 May 2008 Ms 8.0 Wenchuan earthquake, China
abstract: The 12 May 2008 Wenchuan earthquake (Ms 8.0) triggered over 56,000 landslides over a broad area, including shallow, disrupted landslides, rock falls, deep-seated landslides, and rock avalanches. Among these landslides, rock avalanches are of great concern because of the large volume of displaced material, the long runout distance and the resulting fatalities. In this paper, some rock avalanches (including the Woqian, the Tangjiawan, the Hongyancun, the Xiejiadianzi, and the Shuimogou rock avalanches) were selected for detailed study. Mapping of coseismic surface rupture has been carried out at regional and site scales. The minor scarps or stepped topographic features observed at the source areas of the rock avalanches correspond spatially to the surface rupture, indicating that they should be created by thrusting of a fault that ruptured during the 2008 Wenchuan earthquake. Avalanche deposits of some rock avalanches are shifted northeastward, the same direction with the strike–slip of the fault rupture, compared with the sources of the rock avalanches, indicating that the component of strike–slip of the fault rupture exerted a horizontal initial velocity on the failed mass. For the Woqian rock avalanche, the source rock on the hanging wall was pushed northeastward, creating a hummocky topographic feature because of the right-lateral slip of the fault rupture. These rock avalanches are, therefore, triggered by oblique-thrust faulting. In addition, the source rock mass was of poor quality resulting from the shearing and brecciation associated with fault movement in history, rendering the rock slopes prone to failure and contributing to the high degree of disintegration of the failed rock mass.

title: Spatial distribution of landslides triggered by the 2008 Ms 8.0 Wenchuan earthquake, China
abstract: The Ms 8.0 Wenchuan earthquake of May 12, 2008 is one of the most disastrous earthquakes in China. The earthquake triggered tens of thousands of landslides over a broad area, including shallow, disrupted landslides, rock falls, deep-seated landslides, and rock avalanches, some of which buried large sections of some towns and dammed the rivers. The purpose of this study is to investigate correlations between the occurrence of landslides with geologic and geomorphologic conditions, and seismic parameters. Over 56,000 earthquake-triggered landslides, with a total area of 811 km 2 , are interpreted using aerial photographs and remote sensing images taken following the earthquake. The spatial distribution of these landslides is analyzed statistically using both landslide-point density (LPD), defined as the number of landslides per square kilometer, and landslide-area density (LAD), the percentage of the area affected by landslides, to determine how the occurrence of landslides correlates with distance from the epicenter, distance from the major surface rupture, seismic intensity and peak ground acceleration (PGA), slope angle, slope aspect, elevation, and lithology. It is found that both LAD and LPD have strong positive correlations with slope steepness, distance from the major surface rupture and seismic intensity, and that Pre-Sinian schist, and Cambrian sandstone and siltstone intercalated with slate have the most concentrated landslide activities, followed by the Permian limestone intercalated with shale, and Devonian limestone. Statistical analyses also indicate that the major surface rupture has influence on the spatial distribution of landslides, because LAD and LPD are relatively higher on the hanging wall than on the footwall. However, the correlation between the occurrence of landslides with distance from the epicenter of the earthquake is complicated, rather than a relatively simple negative correlation as found from other reported cases of earthquakes. This is possibly due to complicated rupture processes of the earthquake.

title: Interactive terrain visualization enables virtual field work during rapid scientific response to the 2010 Haiti earthquake
abstract: The moment magnitude (Mw) 7.0 12 January 2010 Haiti earthquake is the fi rst major earthquake for which a large-footprint LiDAR (light detection and ranging) survey was acquired within several weeks of the event. Here, we describe the use of virtual reality data visualization to analyze massive amounts (67 GB on disk) of multiresolution terrain data during the rapid scientifi c response to a major natural disaster. In particular, we describe a method for conducting virtual fi eld work using both desktop computers and a 4-sided, 22 m 3 CAVE immersive virtual reality environment, along with KeckCAVES (Keck Center for Active Visualization in the Earth Sciences) software tools LiDAR Viewer, to analyze LiDAR pointcloud data, and Crusta, for 2.5 dimensional surfi cial geologic mapping on a bare-earth digital elevation model. This system enabled virtual fi eld work that yielded remote observations of the topographic expression of active faulting within an ~75-km-long section of the eastern Enriquillo‐Plantain Garden fault spanning the 2010 epicenter. Virtual fi eld observations indicated that the geomorphic evidence of active faulting and ancient surface rupture varies along strike. Landform offsets of 6‐50 m along the Enriquillo‐ Plantain Garden fault east of the 2010 epicenter and closest to Port-au-Prince attest to repeated recent surface-rupturing earthquakes there. In the west, the fault trace is well defi ned by displaced landforms, but it is not as clear as in the east. The 2010 epi center is within a transition zone between these sections that extends from Grand Goâve in the west to Fayette in the east. Within this transition, between L’Acul (lat 72°40′W) and the Rouillone River (lat 72°35′W), the Enriquillo‐Plantain Garden fault is un defi ned along an embayed low-relief range front, with little evidence of recent surface rupture. Based on the geometry of the eastern and western faults that show evidence of recent surface rupture, we propose that the 2010 event occurred within a stepover that appears to have served as a long-lived boundary between rupture segments, explaining the lack of 2010 surface rupture. This study demonstrates how virtual reality‐based data visualization has the potential to transform rapid scientifi c response by enabling virtual fi eld studies and real-time interactive analysis of massive terrain data sets.

title: A Comprehensive Study of the Rational Function Model for Photogrammetric Processing
abstract: The rational function model (RFM) has gained considerable interest recently mainly due to the fact that Space Imaging Inc. (Thornton, Colorado) has adopted the RFM' as an alternative sensor model for image exploitation. The RFM has also been implemented in some digital photogrammetric systems to replace the physical sensor mode for photogrammetric processing. However, there have been few publications addressing the theoretical properties and practical aspects of the RFM until recently. In this paper a comprehensive study of the RFM is reported upon. Technical issues such as the solutions, feasibility, accuracy, numerical stability, and requirements for control information are addressed. Both the direct and iterative least-squares solutions to the RFM are derived, and the solutions under terrain-dependent and terrain-independent computation scenarios are discussed. Finally, evaluations of the numerous tests with different data sets are analyzed. The objective of this study is to provide readers with a comprehensive understanding of the issues pertaining to applications of the RFM.

title: Test and analysis for precision of GPS precise point positioning
abstract: PPP(precise point positioning) is one of the hotspots in GPS research field.The paper introduced its math model and data-processing scheme,described the effects of different IGS products on the solution results and presented the testing process and the data analysis result for PPP in static and dynamic modes.It was verified that this method of PPP could reach the precision of centimeter-level(in WGS-84 coordinate),and the convergence time is generally within 30 min.

title: Paleoseismic events and recurrence interval along the Beichuan–Yingxiu fault of Longmenshan fault zone, Yingxiu, Sichuan, China
abstract: Prior to the 2008 Wenchuan earthquake (Mw 7.9), Sichuan, China, no earthquake of magnitude larger than M 7.0 had been reported in the historical record for the Longmenshan region. To reveal paleoseismic behaviors in this region, we conducted a paleoseismic study along the 2008 Wenchuan earthquake fault scarp at the town of Yingxiu along the Beichuan–Yingxiu fault. Through a trench investigation, geomorphic analysis and radiocarbon dating, we interpret the occurrence of three paleoseismic events (including the Wenchuan earthquake) within the past 6000 years. The cumulative vertical displacement resulting from the three seismic events is ~ 7.6 m. The coseismic uplift for the Wenchuan earthquake is ~ 2.4 m. Integrated with previous paleoseismic results along the fault, the age of the penultimate event is constrained between 3300 and 2300 cal BP. We suggest the antepenultimate event occurred later than 5920–5730 cal BP. An average vertical slip rate of 0.88–0.91 mm/year is calculated from the vertical displacement of U2 since 5940–5730 cal BP. We estimate that an average recurrence interval of large earthquakes is at most 3000 years. Furthermore, the three paleoseismic events revealed at Yingxiu show similar coseismic vertical displacements. We propose that the strain accumulation and deformation across the Longmenshan fault zone is a relatively stable and continuous process since late Quaternary.

title: Slip maxima at fault junctions and rupturing of barriers during the 2008 Wenchuan earthquake
abstract: The devastating Wenchuan earthquake in 2008 struck along a fault zone that showed low rates of deformation. Analysis of GPS and InSAR data suggests that, as structural barriers failed during a single earthquake, the rupture cascaded across multiple fault segments, which may explain the high magnitude of the event.

title: Geomorphic limits to climate-induced increases in topographic relief
abstract: Recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross-disciplinary investigation and debate on the question of whether tectonics have driven long-term climate change or vice versa. It has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision. Because isostasy acts to compensate mean elevations, the debate hinges on the question of whether climate change can significantly increase topographic relief or, more precisely, increase the volume of ‘missing mass’ between summits and ridges. Here we show that, in tectonically active mountain ranges, geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change. Thus, although climate change may cause significant increases in denudation rates, potentially establishing an important feedback between surficial and crustal processes, neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift.