Schmidt Hammer Rebound Values Research Articles

Enhancing geochemical background estimation using rock weathering

The chemical composition of stream sediments is heavily influenced by weathering processes occurring in upstream lithological units. Despite their importance, these processes are frequently ignored in the examination of stream sediment geochemical data when identifying mineralized zones. Instead, existing geochemical background estimation procedures rely on the area size of upstream rocks as an indicator of their contribution to elemental concentrations of sediments. To address this limitation, a stream sediment geochemical survey was conducted in a pilot area in central Iran, and the physico-mechanical properties of upstream rock types, including elastic velocities, porosity, and Schmidt hammer rebound values, were evaluated. A new weathering index, “Wij,” was developed, utilizing proxies of rock weathering to estimate the geochemical background attributed to lithology at sediment sampling sites. The regression model was constructed by combining weathering proxies (Wij) with other independent variables, including the presence or absence of rocks in catchments, area size (Xij), and the weathering-corrected contributing factor (XijWij). The results suggested the significant capability of weathering proxies in explaining the geochemical variability of major elements such as Al, K, Fe, Ca, and Na. However, the regression model using weathering-corrected contributing factors delivered better overall accuracy than other independent variables. Nevertheless, our results also identified some limitations of the application of regression model in stream sediment data analysis.

Building a bimodal landscape: bedrock lithology and bed thickness controls on the morphology of Last Chance Canyon, New Mexico, USA

Abstract. We explore how rock properties and channel morphology vary with rock type in Last Chance Canyon, Guadalupe Mountains, New Mexico, USA. The rocks here are composed of horizontally to near-horizontally interbedded carbonate and sandstone. This study focuses on first- and second-order channel sections, where the streams have a lower channel steepness index (ksn) upstream and transition to higher ksn values downstream. We hypothesize that differences in bed thickness and rock strength influence ksn values, both locally by influencing bulk bedrock strength and also nonlocally through the production of coarse sediment. We collected discontinuity intensity data (the length of bedding planes and fractures per unit area), Schmidt hammer rebound measurements, and measured the largest boulder at every 12.2 m elevation contour to test this hypothesis. Bedrock and boulder mineralogy were determined using a lab-based carbonate dissolution method. High-resolution orthomosaics and digital surface models (DSMs) were generated from drone and ground-based photogrammetry. The orthomosaics were used to map channel sections with exposed bedrock. The United States Geological Survey (USGS) 10 m digital elevation models (DEMs) were used to measure channel slope and hillslope relief. We find that discontinuity intensity is negatively correlated with Schmidt hammer rebound values in sandstone bedrock. Channel steepness tends to be higher where reaches are primarily incising through more thickly bedded carbonate bedrock and lower where more thinly bedded sandstone is exposed. Bedrock properties also influence channel morphology indirectly, through coarse sediment input from adjacent hillslopes. Thickly bedded rock layers on hillslopes erode to contribute larger colluvial sediment to adjacent channels, and these reaches have higher ksn values. Larger and more competent carbonate sediment armors both the carbonate and the more erodible sandstone and reduces steepness contrasts across rock types. We interpret that in the relatively steep, high-level ksn downstream channel sections, the slope is primarily controlled by the coarse alluvial cover. We further posit that the upstream low-level ksn reaches have a base level that is fixed by the steep downstream reaches, resulting in a stable configuration, where channel slopes have adjusted to lithologic differences and/or sediment armor.

Weathering Effects on Engineering Geological Properties of Trachydacitic Volcanic Rocks from the Monte Amiata (Southern Tuscany, Italy)

Variability in lithology and weathering degree affects physical and mechanical properties of rocks. In this study, we investigated the relationships between weathering degree and engineering geological properties of trachydacitic volcanic rocks from Monte Amiata (central Italy) by coupling field and laboratory analyses. We collected in situ Schmidt hammer tests in the field. We evaluated weathering quantifying the percentage of secondary minerals through thermal analysis in the laboratory. We also determined dry density (ρd), specific gravity of solids (Gs), porosity (n) and two-dimensional (2D) porosity as resulted from scanning electron microscopy investigations. The results of our study indicate a negative linear correlation between Schmidt hammer rebound values and secondary mineral percentage. This correlation provides a tool to quantitatively estimate the deterioration of rock uniaxial compressive strength (UCS) as weathering increases. Moreover, thermal analysis turned out to be a quantitative and reproducible method to evaluate weathering degree of magmatic rocks.

Detection of deteriorations in cultural structures created by carving into low-strength rocks by the non-destructive test (NDT) method

In the cultural stone heritage, progressive deteriorations develop over time with the effect of atmospheric processes. These deteriorations can reach to a significant degree that threaten the integrity of the monuments built from weak-strength rocks. In this study, it is aimed to determine the deteriorations caused by atmospheric processes on the monument surface in cultural heritage works built by carving into low-strength pyroclastic rocks by non-destructive tests (NDTs). To this end, two historic structures in the Kilistra Ancient City of Konya (Turkey) were selected. The index, strength, mineralogical and petrographic properties of the rocks, in which the monuments were carved, were first investigated. Then, contour scaling, crack, efflorescence and biodeterioration types were determined on the facades of the monuments. Later, NDT deterioration change maps were prepared based on the data obtained by performing the relative humidity, Schmidt hammer rebound (SHR), and P-wave velocity (Vp) measurements on the facades of the monuments. In the deterioration maps, it was determined that the SHR and Vp values of the rock were low in the capillary, infiltration, and crack zones with water penetration in the monuments built on low-strength pyroclastic rocks. However, deterioration was less in the regions with more limited water access according to zones.

Geological Controls on Marine Cavernous Landforms along Japanese Pacific-side Rocky Coasts

Marine cavernous landforms, including notches, caves, arches and tunnels, characterize the rocky coast landscape and are strongly influenced by the geology (e.g., rock strength and structure) of sea cliffs. Geological controls on the development and shape of marine cavernous landforms are evaluated based on field investigations along the Pacific coastlines of Honshu Island, Japan. Morphological parameters, width (w), depth (d), and height (h), of cavernous landforms were measured directly or through images taken with an unmanned aerial vehicle, together with geological factors, such as rock types, strength (Schmidt hammer rebound values: R), dips and strikes of bedding, major joints, and fault planes. In total, 76 caves are investigated in six coastal areas: Sanriku Coast, Joban Coast, Boso Peninsula, Miura Peninsula, Izu Peninsula, and Kii Peninsula. According to shape index, d/w, and presence of the open end, cavernous landforms are classified into notches (d/w < 1, closed end), caves (d/w ≥ 1, closed end), arches (d/w < 1, open end), and tunnels (d/w ≥ 1, open end). An analysis shows that the major geological controls differ between notches and the other three forms. Low rock strength (R < 40) and sub-horizontal bedding are, respectively, the primary and secondary controls on the formation of notches, whereas weak rock structures (joints, faults and bedding) with a dip steeper than 30° (vertical or steeply inclined structures) and a strike trending perpendicular to the cliff face are the major controls on the formation of caves, arches and tunnels. Rock strength also affects planar forms defined by the shape index, promoting a deepening of cavernous forms, particularly when the cliff has a medium rock strength (R = 30-50) that provides an optimal balance between erosion force and resisting force. In general, vertical or steep structures contribute to the deepening of holes, whereas horizontal or gentle structures favor widening.

Morphological and physical-mechanical characterization of a syenogranite weathering profile developed on tropical climate

In regions of tropical climate weathering processes tend to be very active in engineering time in terms of range and effectives, producing alteration mantles that are often deep and well developed when compared to weathering profiles similar rocks developed on temperate climate. In the municipality of Cachoeiro de Itapemirim, Southeastern Brazil there are many syenogranite weathering profiles on ornamental stone quarries, in which it is possible to observe the effects of weathering at different levels. Considering the importance of knowing the behaviour of these different transition materials in civil and mining engineering design, it becomes relevant to characterize their morphology and physical properties. Among the weathering profiles visited, the focus of this study is a weathering profile that presented the higher heterogeneity, with more alteration levels and better accessibility for sample collection, in situ tests and morphology characterization and description. Samples were collected and the following lab tests were performed for the physical-mechanical characterization: physical indexes (apparent dry density, apparent porosity, absorption capacity and void index), P-wave velocity, Schmidt hammer rebound value and point load index. The preliminary results indicate there is a strong structural control in the development of weathering and that shape of the relief contribute to accelerate the processes of alteration and quick dissection of the relief, avoiding the formation of a profile with more gradual transitions between different weathering levels. As for the physical-mechanical characteristics, a considerable maximum loss of resistance, about 99% in point load index, and maximum increase of the porosity, about 97 %, is observed with the increase on the degree of weathering, being these two parameters more sensitive for the studied granite.

An Experimental Study on Non-Destructive Evaluation of the Mechanical Characteristics of a Sustainable Concrete Incorporating Industrial Waste.

Structural materials sustainability is gaining popularity across the globe at present. Reusing natural resources, building, demolition debris, and solid waste are the most apparent tools to make construction more environmentally friendly. Traditional concrete is believed to be less durable, stronger, environmentally friendly, and socially and commercially feasible than industrial waste concrete. The evolution of non-destructive testing (NDT) across time has not been investigated in depth by researchers. An experimental study was carried out to propose the use of non-destructive mechanisms that would enable us to assess concrete’s compressive strength without causing destruction. Varying quantities of industrial waste (coal bottom ash (CBA) and waste glass sludge (WGS)) were incorporated to cast concrete prisms (150 mm × 150 mm × 150 mm). The results obtained helped us to establish relationships between the compressive strength of concrete and the Schmidt hammer rebound value, as well as the ultrasonic pulse velocities. Microstructural analysis showed that incorporating 10% of CBA and WGS improved the porosity of concrete specimens, which shows the applicability of these industrial wastes as partial cement replacements. Scanning electron microscopy (SEM) showed traces of calcium alumino-silicate hydrate (C-A-S-H), portlandite and C-S-H, which indicates the binder characteristics of CBA and WGS. The concept of the response surface approach (RSM) for optimizing cement and industrial waste substitution was validated by the polynomial work expectation. The model was statistically significant when the fluctuation of ANOVA was analyzed using a p value with a significance level of 0.05. The study results show that the usage of 15% CBA and 10% WGS as a cementitious additive and cement replacement has the potential to increase the strength of concrete significantly.

Application Of Schmidt Hammer Rebound Test For Weathering Profile Classification Of Granite, Paya Terubong, Penang, Malaysia

Weathering profile characterization is one of the significant information in the interpretation of the condition of rock. In addition, the tropical climate in Malaysia causes the deep–seated weathering phenomena of granitic rock. The identification of weathering profile of granite can be made using in–situ Schmidt hammer rebound test which is one of the non–destructive tests (NDT) that is widely used. In this study, the test is carried out on granitic rock in Paya Terubong, Pulau Pinang. Based on the study conducted, the value for each of weathering grade of granite can be identified. The value for fresh granite (Grade I) is greater than 55, slightly weathered granite (Grade II) is ranging from 35 – 55, moderately weathered granite (Grade III) is ranging from 17 – 35 and highly weathered granite (Grade IV) is less than 17. Completely weathered granite (Grade V) and residual soil (Grade VI) do not have any Schmidt hammer rebound values. This method can be used as a very useful method in the field to determine the degree of weathering of rock outcrops.

Macro-mechnical charakteristics and their control on the strenght of sandstones of western Indo-Burmese Rangers, NE India

Mechanically strong sandstones consider as a potential construction material which can withstand modest load and not associated with any geologic fractures. This work is about understanding the macro-mechanical properties of sandstones by studying several petrographic parameters, which could provide evidence of their influence on mechanical strength. Here the authors were considered the Bhuban sandstones of western Indo-Burmese Ranges (IBR) of north-eastern India to investigate the above criteria. The result shows that sandstones have a mean grain size between 108 to 208 μm. Moderate to poorly sorted (phi scale ranges 0.56–1.5) grains show greater content of rounded constituents (43–68 %) with sphericity between 0.65–0.85; along with moderate packing properties (packing density 54–77 %; packing proximity 32–70 %). The grains join by mostly straight (20–54 %) and concavo-convex (13–45 %) contacts; with lesser point (5–13 %) and sutured contacts (8-44 %). Schmidt Hammer rebound values (R-values) were used to calculate and analyse the uniaxial confined stress (UCS); which again validated with UCS testing of core samples. The comparison between macro-mechanical parameters and the UCS shows interrelationship among rock constituents which hold the key to the mechanical strength of the rock. The presence of angular grains and semi-angular spherical grains diminish the macro-mechanical strength to some extent. Moreover, FETEM-EDX analysis confirms the micro-weathering of the angular grains, which have a deformed lattice setting. These findings show that macro-mechanical and micro-nano scale properties of sandstones influence the rock strength.

Indirect Estimation of Rock Uniaxial Compressive Strength from Simple Index Tests: Review and Improved Least Squares Regression Tree Predictive Model

Uniaxial compressive strength is an important mechanical parameter for rock mass engineering. Hence, how to determine the UCS simply and accurately have drew numerous attention. In this paper, the references related to UCS estimation using indirect tests were reviewed, and three stages of the development of indirect UCS estimation were classified. Meanwhile, the merits and drawbacks of different kinds of indirect tests for evaluating UCS were analyzed, and a indirect parameter (Schmidt hammer rebound value (L-type)) was determined to estimate the UCS values. For establishing more precise predictive model, more than 700 groups of data set were collected from 20 references. Subsequently, the improved least squares tree algorithm was utilized to establish the predictive model. The fitting coefficients indicated that the predictive model can be applied to engineering practice.

Accurate performance prediction model for impact hammer developed using customized evolutionary algorithm

In past decades, impact hammers have played a key role in underground construction. Simply in Istanbul, impact hammers have been used to excavate more than 20 km of metro tunnels. Thus, determining the instantaneous breaking rate (IBR) of an impact hammer is attracting increasing attention. A number of IBR prediction models have been developed for impact hammers. However, there is still a demand for models that require a smaller number of easy-to-obtain rock properties as inputs and provide a reasonable level of accuracy, a wide range of applications, and high reliability. This study had the goal of developing such a prediction model based on an investigation of two subway tunnels built in Istanbul. In order to enhance the results generated by multiple linear regression analysis, a customized tool was developed for the non-linear analysis of a relatively large set of data collected for the present research. Gene expression programming (GEP) and particle swarm optimization (PSO) were merged to create a non-linear analysis tool. The GEP–PSO algorithm was trained using 80% of the available data, with the remaining 20% reserved to validate the results. The output of the algorithm was presented in the form of a mathematical equation that predicted the IBR using the uniaxial compressive strength, rock quality designation, Schmidt hammer rebound value, and machine power as input parameters. The predicted IBR values were in remarkable agreement with the recorded values. In order to verify the efficiency of the proposed prediction model, it was successfully tested against previously developed models for which input parameters were available. In addition, the proposed model was investigated under hypothetical circumstances to ensure that it legitimately described the performance changes due to changes in the input parameters. The model developed in this research is proposed as an accurate and reliable tool for predicting the performance of impact hammers over a wide application range.

Clast transport history influences Schmidt hammer rebound values

AbstractThe Schmidt hammer (SH) is widely used in geomorphology for relative‐ and calibrated‐exposure age dating surfaces and deposits within landforms. This study employs a laboratory‐based methodology to assess the effects of surface roughness, clast roundness, and clast volume on SH rebound values (R‐values) by analyzing samples from three modern depositional environments (i.e. river, alluvial fan, talus). Each environment contains clasts of Torlesse supergroup greywacke sandstones with distinct roundness and micro‐scale roughness characteristics. Roundness, surface roughness, and clast volume were all found to influence R‐values significantly. The R‐values from different deposit types are statistically significant and could potentially create an apparent age divergence of several thousand years for samples with the same exposure‐age. © 2020 John Wiley &amp; Sons, Ltd.

Schmidt hammer and terrestrial laser scanning (TLS) used to detect single‐event displacements on the Pleasant Valley fault (Nevada, USA)

ABSTRACTChanges in surface roughness on carbonate fault scarps often reflect varying durations of subaerial weathering. On the Pleasant Valley fault in central Nevada, the documentation of a surface rupture in 1915, a long recurrence interval of faulting, slow weathering rate, and a relatively high (2–3 m) single‐event displacement make the discrimination of the historical and penultimate slip patches unambiguous. Following from a 2018 study, we used a Schmidt hammer and terrestrial laser scanning (TLS) to further test whether these weathering patterns delineate exposed slip patches on a fault scarp. Results show that Schmidt hammer rebound value ranges (termed ΔR – the difference between minimum and maximum R‐values in repeat impacts at a point), increase by ~8–10 points across the historical–penultimate event transition zone in two separate scarp transects. TLS‐derived surface roughness also indicates a clear difference between the most recent and penultimate events. The average single‐event displacement (SED) estimated using the Schmidt hammer and TLS is 2.85 m at two transect sites and is roughly equivalent to the visually estimated 3 m. While this fault is an ideal case where we know some of the slip history, the results demonstrate that these techniques show promise for discriminating slip patches on larger carbonate fault scarps with longer paleoearthquake histories, and could be used alongside 36Cl cosmogenic exposure‐age dating to improve paleoseismic records on normal faults. © 2019 John Wiley &amp; Sons, Ltd.

A new empirical formula for evaluating uniaxial compressive strength using the Schmidt hammer test

The uniaxial compressive strength (UCS) of rock is an important geotechnical parameter for engineering applications. However, how to determine the UCS simply and accurately has drawn the attentions of may researchers. To date, different kinds of indirect methods have been invented to determine the UCS of rocks, and among these methods, estimation of the UCS based on the Schmidt hammer rebound value (Hr) was commonly adopted. In this paper, an insightful analysis of the literature related to UCS estimation using the Schmidt hammer test was conducted, and three stages for the development of UCS estimation using Hr were classified. The drawbacks and merits of different kinds of techniques were analyzed in detail. Then, a data set containing the data for different rock types was collected from references, and to obtain an objective empirical formula, the simulated annealing-gene expression programming (SA-GEP) method was employed to establish the correlation between UCS and Hr. Based on the calculation results, the L-type Schmidt hammer was suggested for use in UCS estimation, and the corresponding empirical formula was established. To confirm validity of the empirical formula, the Schmidt hammer tests and uniaxial compressive tests were conducted separately, the experimental results were in a good agreement with the proposed empirical formula, implying that the proposed empirical formula can be applied in engineering practice.

Examine the Correlation between Physico-Mechanical properties of Selected Granite rocks in Ondo State, Nigeria

This research examines the correlation between physico-mechanical properties of some selected granite rocks in Ondo State, Nigeria. Samples were collected at Zibo FM Quarry, Aaye and Samchase Quarry, Itaogbolu and tested in the laboratory for the determination of rock density, hardness, and strength. An average density of between 2.57g/cm3 and 2.67g/cm3 was recorded. Schmidt hammer and Rockwell hardness machine wereused for the determination of rock samples hardness. An average uniaxial compressive strength of rock sample was estimated from the values obtained from Schmidt hammer rebound value. The Hardness test varies from 115.90MPa to 185.00MPa (classified to have high strength) while the average Rockwell hardness varied from 45.1HRA - 57.32HRA. The average point load index ranges from 7.402MPa - 7.505MPa classified to have very high strength. Multiple regression analysis using computer-aided solution (Statistical Package for Social Sciences - SPSS) was used to analyze data obtained from the laboratory and field tests. Five parameters were input into the multiple regression analysis to generate the models. Two parameters which are Schmidt hammer rebound value and Rockwell hardness value out of five parameters are dependent variables, while point load index, uniaxial compressive strength, and density are independent variables. The result of the models developed shows positive correlations – an indication that the hardness of rock gives a significant contribution in drilling bit selection. Keywords : Rock density, Schmidt hardness, Rockwell hardness, uniaxial compressive strength, point load strength, and SPSS

Investigation of engineering properties for usability of Lefke stone (Osmaneli/Bilecik) as building stone

Lefke stone is a sandstone that has been widely used in mosques, madrasas, churches, and houses as building stone. The geological features and engineering properties of Lefke stone outcropped in the southern part of Osmaneli/Bilecik were investigated in field and laboratory studies. Samples acquired during the fieldwork were tested to determine the physical, mechanical, durability, and hygrothermal properties in the laboratory. The mean physico-mechanical properties of Lefke stone yielded apparent density of 2.38 g/cm3, specific gravity of 2.68 g/cm3, total porosity of 11.26%, 2.93% water absorption by weight, uniaxial compressive strength of 94 MPa, flexure strength of 11.45 MPa, a 3.90 MPa point load strength, 4.5–5 Mohs hardness, and field Schmidt hammer rebound value of 36. According to durability tests, Lefke stone is resistant to CaCl2 salt mist but has low resistance to SO2 aging. Salt crystals placed in the discontinuities of the rock caused slight crack growth. The stone’s resistance to crystallization of sodium sulphate salt is low, and an increase in the volume of salts crystallized in the rock results in low corner strengths. A capillary water-absorption value of 0.0016 kg/m2.h places Lefke stone into the category of very low water absorption capacity and permeability. The water vapor diffusion resistance factor (μ) less than 1 indicates that the sandstone has high breathability. Its performance in historical buildings, field observations, and values obtained through laboratory tests confirm that Lefke sandstone can be used as a building stone.

Post-blast Non-destructive Damage Assessment on Full-scale Structural Elements

A damage assessment methodology, based on the Schmidt hammer rebound value, has been developed and applied to evaluate the integrity of different structural elements after a blast event. All the elements (nine slabs, five beams and four masonry walls) were tested at full-scale with scaled distances that range from 0.2 to 2.92 m/kg1/3. The methodology consists of the evaluation of a statistically significant difference between six rebound values before and six after a blast event at each evaluation point. Based on each individual damage value, damage maps have been created using an interpolation tool. The combination of a global damage value with the spalled area based on visual inspection, allows the comparison between different protective solutions against blasting. The methodology presented and validated in this work can be used to evaluate the status of different concrete elements after a blast event such as terrorist attacks and can be also used for determination of the quality of different protective solutions. In terms of the solutions tested, the use of fibers enhances the tensile resistance of specimens. Concrete in beams configuration appears to have less resistance than in slabs, making them more vulnerable against explosives. To reduce the inner spalling in tiling wall areas, and the associated injuries, a good potential solution is the basalt fiber mesh.

Experimental investigation on the performance of Schmidt hammer test in durability assessment of carbonate building stones against freeze–thaw weathering

Although Schmidt hammer test has been widely used for assessment of weathering state of rocks, its application for evaluation of rock durability remains rare. This study aims at investigating the performance of the Schmidt hammer test in the durability assessment of carbonate building stones against frost weathering. For this purpose, nine types of carbonate rocks were collected from various quarries of Iran and subjected to a series of tests including determination of petrographical, physical, mechanical, ultrasonic, and rebound hardness properties. Moreover, long-term weathering test of freeze–thaw, up to 100 cycles, were carried out and ultrasonic detection was used to detect the weathering-induced damages of rocks. In ultrasonic detections, ultrasonic parameters of maximum amplitude (Amax), spatial attenuation (αs), and compressional wave velocity (Vp) were determined before and after freeze–thaw tests and then their change rates were determined. The change rates of Amax, αs, and Vp including KA, Kα, and KP, respectively, were considered as the functions of the degree of the frost-induced damages of rocks, and consequently as indications of the rock durability. Results showed that there are close correlations between the Schmidt hammer rebound value (Rn) and KA, Kα, and KP. However, the correlation between Rn and KP was weaker than those between Rn and KA and Kα because of the disproportionate response of Vp to the rock deterioration. It was concluded that the Schmidt hammer test is capable to evaluate the durability of carbonate building stones and can be used for a rapid and onsite evaluation of rock durability at different quarry faces. Hence, it allows selecting more durable rocks for different applications in new constructions and also in replacement works in historical sites.

Detection of internal defects of concrete structures based on statistical evaluation of healthy part of concrete by the noncontact acoustic inspection method

A noncontact acoustic inspection method was developed to perform measurements from a long distance (usually about 5 to 7 m but even over 30 m) and detect internal defects (up to 10 cm in depth) of concrete structures using a long-range acoustic device and a laser Doppler vibrometer. An algorithm was also proposed to detect internal defects of concrete by combining two acoustic features, the vibrational energy ratio and spectral entropy obtained by our measurement. However, in actual concrete structures, it is difficult to distinguish a boundary between a healthy part and a defective part owing to influences such as the shape of internal defects, age-induced deterioration, and the surface condition of concrete. Therefore, we propose a method to statistically evaluate the distribution of the healthy part of concrete and extract the healthy part to identify the defective part. By this proposed method, the actual concrete floor slab bridge was measured from 33 m away and some internal defects were detected and visualized. Furthermore, a result for a railroad tunnel was compared with the Schmidt hammer rebound value and elastic wave velocity to verify the validity of the proposed method.

Field estimate of paleoseismic slip on a normal fault using the Schmidt hammer and terrestrial LiDAR: Methods and application to the Hebgen fault (Montana, USA)

AbstractThe weathering characteristics of bedrock fault scarps provide relative age constraints that can be used to determine fault displacements. Here, we report Schmidt hammer rebound values (R‐values) for a limestone fault scarp that was last exposed in the 1959 Mw 7.3 Hebgen Lake, Montana earthquake. Results show that some R‐value indices, related to the difference between minimum and maximum R‐values in repeated impacts at a point, increase upward along the scarp, which we propose is due to progressive exposure of the scarp in earthquakes. An objective method is developed for fitting slip histories to the Schmidt hammer data and produces the best model fit (using the Bayesian Information Criterion) of three earthquakes with single event displacements of ≥ 1.20 m, 3.75 m, and c. 4.80 m. The same fitting method is also applied to new terrestrial LiDAR data of the scarp, though the LiDAR results may be more influenced by macro‐scale structure of the outcrop than by differential weathering. We suggest the use of this fitting procedure to define single event displacements on other bedrock fault scarps using other dating techniques. Our preliminary findings demonstrate that the Schmidt hammer, combined with other methods, may provide useful constraints on single event displacements on exposed bedrock fault scarps. Copyright © 2018 John Wiley &amp; Sons, Ltd.