We thank Erin Bradley and Liz Cole for their assistance in the field. Field work, thin-section preparation and material for the sandbox model was supported by Franklin &amp; Marshall College's Committee on Grants.

<ol><li>Marshak, S., Wilkerson, M. S., Hsui, H. T. Generation of curved fold-thrust belts: Insights from simple physical and analytical. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aMarshak%2C+S+%22modelsThrust+Tectonics%22">modelsThrust Tectonics</a>. KR, M. cC. lay , Chapman and Hall. 83-92 (1992).</li>
<li>Mitra, G. Evolution of salients in a fold-and-thrust belt: the effects of sedimentary basin geometry, strain distribution and critical taper. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aMitra%2C+G+%22Evolution+of+Geological+Structures+in+Micro-+to+Macro-scales%22">Evolution of Geological Structures in Micro- to Macro-scales</a>. S, S. engupta , Chapman and Hall. 59-90 (1997).</li>
<li>Weil, A., Sussman, A. Classifying curved orogens based on timing relationships between structural development and vertical axis rotations. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aWeil%2C+A+%22Orogenic+curvature+Geol.+Soc.+of+Am.+Special+Paper%22">Orogenic curvature Geol. Soc. of Am. Special Paper</a>. A, S. ussman, A, W. eil 383, 205-223 (2004).</li>
<li>Ismat, Z., Mitra, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Folding+by+cataclastic+flow+at+shallow+crustal+levels+in+the+Canyon+Range%2C+Sevier+orogenic+belt%2C+west-Central+Utah%5BTitle%5D)+AND+%22J.+of+Struct.+Geol%22%5BJournal%5D)">Folding by cataclastic flow at shallow crustal levels in the Canyon Range, Sevier orogenic belt, west-Central Utah.</a> J. of Struct. Geol. 23 (2-3), 355-378 (2001).</li>
<li>Tull, J., Holm, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Structural+evolution+of+a+major+Appalachian+salient-recess+junction%3A+Consequences+of+oblique+collisional+convergence+across+a+continental+margin+transform+fault%5BTitle%5D)+AND+%22Geol.+Soc.+of+Am.+Bull%22%5BJournal%5D)">Structural evolution of a major Appalachian salient-recess junction: Consequences of oblique collisional convergence across a continental margin transform fault.</a> Geol. Soc. of Am. Bull. 117 (3), 482-499 (2005).</li>
<li>Ismat, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Block+supported+cataclastic+flow+within+the+upper+crust%5BTitle%5D)+AND+%22J.+of+Struct.+Geol%22%5BJournal%5D)">Block supported cataclastic flow within the upper crust.</a> J. of Struct. Geol. 56, 118-128 (2013).</li>
<li>Ismat, Z., Toeneboehn, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Deformation+along+a+salient-transverse+zone+junction%3A+An+example+from+the+Leamington+transverse+zone%2CUtah%2C+Sevier+fold-thrust+belt+%28USA%29%5BTitle%5D)+AND+%22J.+of+Struct.+Geol%22%5BJournal%5D)">Deformation along a salient-transverse zone junction: An example from the Leamington transverse zone,Utah, Sevier fold-thrust belt (USA).</a> J. of Struct. Geol. 75, 60-79 (2015).</li>
<li>Reed, F. S., Mergner, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Preparation+of+Rock+Thin+Sections%5BTitle%5D)+AND+%22Amer.+Mineral%22%5BJournal%5D)">Preparation of Rock Thin Sections.</a> Amer. Mineral. 38, 1184-1203 (1953).</li>
<li>Underwood, E. E. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aUnderwood%2C+EE+%22Quantitative+Stereology%22">Quantitative Stereology</a>. , Addison-Wesley Publishing Company. (1970).</li>
<li>Fry, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Random+point+distribution+and+strain+measurement+in+rock%5BTitle%5D)+AND+%22Tectonophys%22%5BJournal%5D)">Random point distribution and strain measurement in rock.</a> Tectonophys. 60 (1), 89-105 (1979).</li>
<li>McNaught, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Estimating+uncertainty+in+normalized+Fry+plots+using+a+bootstrap+approach%5BTitle%5D)+AND+%22J.+of+Struct.+Geol%22%5BJournal%5D)">Estimating uncertainty in normalized Fry plots using a bootstrap approach.</a> J. of Struct. Geol. 24 (2), 311-322 (2002).</li>
<li>De Paor, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+Interactive+Program+for+Doing+Fry+Strain+Analysis+on+the+Macintosh+Microcomputer%5BTitle%5D)+AND+%22J.+of+Geol.+Ed%22%5BJournal%5D)">An Interactive Program for Doing Fry Strain Analysis on the Macintosh Microcomputer.</a> J. of Geol. Ed. 37 (3), 171-180 (1989).</li>
<li>Ismat, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Folding+kinematics+expressed+in+fracture+patterns%3A+An+example+from+the+Anti-Atlas+fold-belt%2C+Morocco%5BTitle%5D)+AND+%22J.+of+Struct.+Geol%22%5BJournal%5D)">Folding kinematics expressed in fracture patterns: An example from the Anti-Atlas fold-belt, Morocco.</a> J. of Struct. Geol. 30 (11), 1396-1404 (2008).</li>
<li>Reches, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Faulting+of+rocks+in+three-dimensional+strain+fields%3A+II.+Theoretical+analysis%5BTitle%5D)+AND+%22Tectonophys%22%5BJournal%5D)">Faulting of rocks in three-dimensional strain fields: II. Theoretical analysis.</a> Tectonophys. 95 (1-2), 133-156 (1983).</li>
<li>Reches, Z., Dieterich, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Faulting+of+rocks+in+three+dimensional+strain+fields%3A+1.+Failure+of+rocks+in+polyaxial%2C+servo-control+experiments%5BTitle%5D)+AND+%22Tectonophys%22%5BJournal%5D)">Faulting of rocks in three dimensional strain fields: 1. Failure of rocks in polyaxial, servo-control experiments.</a> Tectonophys. 95 (1-2), 111-132 (1983).</li>
<li>Ismat, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evolution+of+fracture+porosity+and+permeability+during+folding+by+cataclastic+flow%3A+Implications+for+syntectonic+fluid+flow%5BTitle%5D)+AND+%22Rocky+Mount.+Geol%22%5BJournal%5D)">Evolution of fracture porosity and permeability during folding by cataclastic flow: Implications for syntectonic fluid flow.</a> Rocky Mount. Geol. 47 (2), 133-155 (2012).</li>
<li>Kwon, S., Mitra, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Three-dimensional+kinematic+history+at+an+oblique+ramp%2C+Leamington+zone%2C+Sevier+belt%2C+Utah%5BTitle%5D)+AND+%22J.+of+Struct.+Geol%22%5BJournal%5D)">Three-dimensional kinematic history at an oblique ramp, Leamington zone, Sevier belt, Utah.</a> J. of Struct. Geol. 28 (3), 474-493 (2006).</li>
<li>Casas, A. M., Simon, J. L., Seron, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Stress+deflection+in+a+tectonic+compressional+field%3A+A+model+for+the+northeastern+Iberian+chain%2C+Spain%5BTitle%5D)+AND+%22J.+of+Geophys.+Res%22%5BJournal%5D)">Stress deflection in a tectonic compressional field: A model for the northeastern Iberian chain, Spain.</a> J. of Geophys. Res. 97, 7183-7192 (1992).</li>
<li>Apotria, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Thrust+sheet+rotation+and+out-of-plane+strains+associated+with+oblique+ramps%3A+An+example%5BTitle%5D)+AND+%22J.+of+Struct.+Geol%22%5BJournal%5D)">Thrust sheet rotation and out-of-plane strains associated with oblique ramps: An example.</a> J. of Struct. Geol. 17 (5), 647-662 (1995).</li>
<li>Hubbert, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Theory+of+Scale+Models+as+Applied+to+the+Study+of+Geological+Structures%5BTitle%5D)+AND+%22Geol.+Soc.+of+Am.+Bull%22%5BJournal%5D)">Theory of Scale Models as Applied to the Study of Geological Structures.</a> Geol. Soc. of Am. Bull. 48 (10), 1459-1520 (1937).</li>
<li>Schöpfen, M. P. J., Steyrer, H. P. Experimental modeling of strike-slip faults and the self-similar behavior. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aSch%C3%B6pfen%2C+MPJ+%22Tectonic+Modeling%3A+A+volume+in+honor+of+Hans+Ramberg+Geol.+Soc.+of+Am.+Mem%22">Tectonic Modeling: A volume in honor of Hans Ramberg Geol. Soc. of Am. Mem</a>. Koyi, H. A., Mancktelow, N. 193, 21-27 (2001).</li>
<li>Kwon, S., Mitra, G. Strain distribution, strain history and kinematic evolution associated with the formation of arcuate salients in fold-thrust belts: the example of the Provo salient, Sevier orogeny, Utah. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aKwon%2C+S+%22Orogenic+curvature+Geol.+Soc.+of+Am.+Special+Paper%22">Orogenic curvature Geol. Soc. of Am. Special Paper</a>. Sussman, A., Weil, A. 383, 205-223 (2004).</li>
<li>Elliott, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+motion+of+thrust+sheets%5BTitle%5D)+AND+%22J.+of+Geophys.+Res%22%5BJournal%5D)">The motion of thrust sheets.</a> J. of Geophys. Res. 81, 949-963 (1976).</li>
</ol>

The authors have nothing to disclose.

The Central Utah segment of the Sevier fold-thrust belt, and its northern boundary, the Leamington transverse zone serves as an ideal natural laboratory for studying salient-recess junctions (Figure 1). Along this junction, the transport direction remains constant and the thrust sheets are uninterrupted across the junction, so the only variable is the underlying basement geometry5.
Here, we present a method to analyze this type of salient-recess junction by combining multi-scale fault data collected in the field with a push-block sandbox model, which replicates the large-scale geometry of the field area. The sandbox model experiment represents a longer time period of deformation than the mesoscale fault sets &#8212; we assume that the youngest fault sets accommodated the observed fold geometry. So, the sandbox model, in conjunction with the faults sets, can be used to track thrust sheet deformation and determine details of the underlying basement geometry.
In order for this combined approach to be successful, the following critical steps need to be taken in the field and sandbox experiment. For the field portion, it is critical to determine the scale of fault homogeneity &#8212; fault sets that are not preserved at equivalent scales cannot be directly compared. In addition, a large population of faults (&#8805; 30 fault sets) need to be measured in order ensure statistically reliable data sets9. Moreover, faults should be measured away from heterogeneities, such as bedding contacts, in order to avoid local strain variations. Even microscale variations, such as impurities, a range in grain size and large amount of strain (Fry &#62; 1.8) may influence mesoscale fracture development by creating foliation planes and other heterogeneities. For the experimental portion, the sandbox model must mimic the field geometry as closely as possible. It is recommended that the box be constructed at a larger scope than the field area, in order to avoid edge-effect complications. The macroscale Regions were also enlarged, for the same reason. It is important that the grain size of the sand mimics Coulomb behavior20 &#8212; an average grain size of ~0.5 mm is recommended21. Finally, once the experiment is being run, it is critical that the large scale faults and folds form in the same orientations and order (e.g., forward breaking, backward breaking, etc.) as observed in the field. Otherwise, the structures formed in the model cannot be compared to the field data, even if they look similar.
The results from this study are comparable to, and support, previous work conducted in this area based on FEM17,22, and provides more details to the kinematic history. This suggests that detailed fault data, measured in areas that have deformed by elastico-frictional mechanisms, can be used to develop more detailed kinematic models than some computer models. Although fault data collection and analyses is laborious and time consuming, this method may be more accessible than computer and analog modeling, and is less expensive. Fractures and faults are often overlooked23 &#8212; many geologists view upper crustal deformation as minor and void of patterns. However, a large portion of the crust &#8212; the upper ~15 km&#160;&#8212; deforms by faulting and other elastico-frictional mechanisms. This work suggests that a significant amount of geologic history is stored in the upper crust and is readily available for analysis.
We demonstrate that even in the simplest cases, such as examined here, the structures preserved in the upper crust do not necessarily mimic the underlying basement geometry. Detailed fault analyses can reveal subtleties that may not be revealed with map patterns, standard conjugate fault studies and/or computer models, such as FEM. Using a sandbox model can help explain why some of these subtle patterns exist. This method presented here is simple, reliable and easy to replicate. It can potentially change how many geologists perceive the role of faults and cataclastic flow, and what they can tell us. This method can be used to re-examine, and uncover more kinematic details, of underexplored field areas, and can be easily modified to accommodate geologic settings other than fold-thrust belts. This approach has far reaching implications in terms of tracking fracture controlled fluid flow in the upper crust as well as how fold-thrust belts maintain critical taper at salient-recess junctions.
The main weakness of this approach is that sandbox modeling may not be able to replicate complex geologic histories. For example, in cases where there are variable shortening directions, the timing and direction of events should be carefully tracked in the field and then replicated with different push-blocks in the sandbox model. However, the sand will likely not preserve these various directions of shortening because the sand will flow and bedding layers will not be maintained. This problem may be resolved by adding oil or petroleum jelly to the sand, to make the sand more cohesive. But, then the sand will not behave as a Coulomb material and thus, may not model deformation in the upper crust. Further work is required to unravel more complex natural systems, such as situations where the basement geometry not the only variable.

Fold-thrust belts are composed of salients (or segments), where the thrust sheets in adjoining salients are decoupled by recesses or transverse zones1,2,3. The transition from salient to recess may be markedly complex, involving a multifaceted suite of structures, and may hold critical clues to fold-thrust belt development. In this paper, we carefully examine a salient-recess junction, using a combination of multiscale field data and a sandbox model, in order to better understand how deformation can be accommodated within fold-thrust belts.
The junction of the Central Utah segment and the Leamington transverse zone is an ideal natural-laboratory for studying salient-recess junctions for several reasons (Figure 1). First, the rocks exposed within the segment continue, uninterrupted, into the transverse zone4. So, deformation patterns can be tracked continuously, and compared across the junction. Second, the rocks are essentially monomineralic, so variation in fault patterns are not a result of heterogeneities within units, but instead reflect the overall folding and thrusting within the study area4. Third, elastico-frictional mechanisms, such as cataclastic flow, assisted deformation throughout the field area, allowing for direct comparisons of mesoscale fault patterns4. Finally, the overall transport direction remained continuous along the length of the segment and transverse zone; therefore, variations in shortening direction did not influence the preserved deformation patterns4. All of these factors minimize the number of variables that may have affected the deformation along the segment and transverse zone. As a result, we surmise that the preserved structures formed primarily because of a change in the underlying basement geometry5.
<img alt="Figure 3" src="/files/ftp_upload/54318/54318fig1.jpg" /> 
Figure 1. Example of index map. The Sevier fold-thrust belt of western USA, showing major salients, segments, recesses and transverse zones. Figure 2 indicated by boxed area (modified from Ismat and Toeneboehn7). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54318/54318fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Folding and thrusting within the Central Utah segment and Leamington transverse zone, took place at depths &#60; 15 km, i.e., within the elastico-frictional regime, where deformation occurred primarily by outcrop-scale (&#60; 1 m) faults and cataclastic flow4,6. Because transport and folding of the thrust sheet took place primarily by elastico-frictional mechanisms, we predict that a detailed fault analysis can provide further insight into the kinematic history of the Leamington transverse zone and the underlying basement geometry. In order to test this hypothesis, we have collected and analyzed fault patterns preserved in the rocks within the northern portion of the Central Utah segment and throughout the Leamington transverse zone (Figure 2).
<img alt="Figure 3" src="/files/ftp_upload/54318/54318fig2.jpg" /> 
Figure 2. Example of macroscale topographic map. Shaded-relief topographic map of boxed area in Figure 1. The 4 Regions are separated by solid white lines. Bedding contacts between the Proterozoic Caddy Canyon quartzite (PCc), Proterozoic Mutual quartzite (PCm) and Cambrian Tintic quartzite (Ct) are shown. Dashed lines show the trend of the mountains within this area. Site locations are shown with numbered black squares. First-order lineations are shown with solid gray lines (modified from Ismat and Toeneboehn7). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54318/54318fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Sandbox experiments were carried out to compare against, and supplement, the fault data. A push-block sandbox model, with frontal and oblique ramps, was used to assist our analyses of the structures preserved in, and around, the Leamington transverse zone (Figure 3) 7. The objectives of this approach are four-fold: 1) determine if the mesoscale fault patterns are consistent, 2) determine if the sandbox model supports and explains the field data, 3) determine if the sandbox model provides more details on structures that are not observed in the field, and 4) evaluate whether this combined field-experimental method is useful and easy to replicate.
<img alt="Figure 3" src="/files/ftp_upload/54318/54318fig3.jpg" /> 
Figure 3. Example of push-block model. Photograph of empty sandbox model. The southern frontal ramp (SFR), oblique ramp (OR), northern frontal ramp (NFR), and the four Regions (1-4) are labeled (modified from Ismat and Toeneboehn7). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54318/54318fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table><tbody><tr><td>fiberboard</td><td>Any</td><td>NA</td><td></td></tr><tr><td>finishing lacquer</td><td>Any</td><td>NA</td><td></td></tr><tr><td>epoxy</td><td>Epoxy technology</td><td>Parts A and B: 301-2 2LB</td><td>Best if warmed to 80&amp;ordm; - 125&amp;ordm;. If warming is not possible, it will cure fine, it will just take 1 week, rather than 1 day.</td></tr><tr><td>ramp wood-pine</td><td>Any</td><td>NA</td><td></td></tr><tr><td>painters tape</td><td>Any</td><td>NA</td><td></td></tr><tr><td>rabbit joints</td><td>Any</td><td>NA</td><td></td></tr><tr><td>countersunk fasteners</td><td>Any</td><td>NA</td><td></td></tr><tr><td>sand paper</td><td>Any</td><td>NA</td><td></td></tr><tr><td>play sand</td><td>Any</td><td>NA</td><td>best if homogenous grain size, ~0.5 mm</td></tr><tr><td>food coloring</td><td>Any</td><td>NA</td><td>best to use one color and a dark color</td></tr><tr><td>plastic mesh/grid</td><td>Any</td><td>NA</td><td></td></tr><tr><td>square cross oins</td><td>Any</td><td>NA</td><td></td></tr><tr><td>crank screw</td><td>Any</td><td>NA</td><td></td></tr><tr><td>crank handle</td><td>Any</td><td>NA</td><td></td></tr><tr><td>sheet metal</td><td>Any</td><td>NA</td><td></td></tr><tr><td>dividers bars</td><td>Any</td><td>NA</td><td></td></tr></tbody></table>

kinematic history of a salient-recess junction explored through a combined approach of field data and analog sandbox modeling

Within fold-thrust belts, the junctions between salients and recesses may hold critical clues to the overall kinematic history. The deformation history within these junctions is best preserved in areas where thrust sheets extend from a salient through an adjacent recess. We examine one such junction within the Sevier fold-thrust belt (western United States) along the Leamington transverse zone, northern Utah. Deformation within this junction took place by faulting and cataclastic flow. Here, we describe a protocol that examines these fault patterns to better understand the kinematic history of the field area. Fault data is supplemented by analog sandbox experiments. This study suggests that, in detail, deformation within the overlying thrust sheet may not directly reflect the underlying basement structure. We demonstrate that this combined field-experimental approach is easy, accessible, and may provide more details to the deformation preserved in the crust than other more expensive methods, such as computer modeling. In addition, the sandbox model may help to explain why and how these details formed. This method can be applied throughout fold-thrust belts, where upper-crustal rocks are well preserved. In addition, it can be modified to study any part of the upper crust that has been deformed via elastico-frictional mechanisms. Finally, this combined approach may provide more details as to how fold-thrust belts maintain critical-taper and serve as potential targets for natural resource exploration.

Aerial photographs were used to subdivide the field area into four Regions (1-4), based on the trend of the modern mountain ridge crest (Figure 2). Multi-scale fault data is compared between these four Regions. Assuming that these trend changes reflect the underlying basement geometry, the oblique ramp is positioned within Regions 2 and 3, where the mountains trend oblique to the Sevier fold-thrust belt. Throughout the four Regions, we found that the mesoscale faults preserve a deformation fabric that is penetrative and homogeneous at the mesoscale (i.e., cubic meter of rock) and are representative of areas larger than the cubic meter sites (Figure 4) 4,16. In addition, microscale variations, shown in Table 1, are not reflected in the collective character of fault patterns. So, the mesoscale fault sets can be directly compared throughout all four Regions (Figure 5). In brief, we found that the mesoscale faults sets can be defined as conjugate-conjugate sets and rotate with bedding, which entail that the shortening directions do, too. This pattern suggests that the mesoscale faults formed early, and different combinations of fault sets are used to assist the fold shape. In more detail, we found that the fault patterns are unique within each of the four regions &#8212; Regions 2 and 3, and Regions 1 and 4, are similar to each other (Figure 6). This pattern supports the macroscale assumption that the oblique ramp underlies Regions 2 and 3, and suggests that our conjugate-conjugate fault analysis is reliable. Beyond that, however, this method of analysis is not any more illuminating. Because of this, we further analyzed the fault data by examining the Equal-area net fault-pole concentrations (Figure 5). This approach is used to track which of the youngest sets were most dominant during deformation. These patterns also suggest an oblique ramp underlying Regions 2 and 3, and unlike the conjugate-conjugate fault analysis, reveal a sharp break between these two Regions. Therefore, we interpret that this pole-concentration analysis is reliable and potentially elucidates subtle structures that may not be clear from the conjugate-conjugate fault method.
Similar to previous models, based on finite element modeling (FEM) we have assumed that the oblique ramp is continuous17. The sharp break in bedding and fault patterns across the boundary between Regions 2 and 3 can be explained by differential motion over a continuous oblique ramp. Alternatively, the discontinuity in bedding and fault patterns across Regions 2 and 3 may reflect a break in the underlying basement. Here, we compare our field data to our sandbox model results in order to test these two hypotheses. We found that a break in the overlying thrust sheet formed even though there was no break in the basement (Figure 10). Interestingly, the location and orientation of the break is comparable to the position and orientation of the boundary between Regions 2 and 3 on the macroscale maps. Therefore, the break observed in the overlying thrust sheet may have simply formed via a complex interaction of an eastward moving thrust sheet over an oblique ramp. In other words, deformation preserved in thrust sheets may not directly mirror the underlying basement geometry. So, this sandbox experiment successfully replicates, and potentially explains, fault patterns preserved in the field.
The epoxied sandbox samples were analyzed from the sandbox model to observe the internal structure of the deformed sand, and compare these structures against field observations. Two representative samples were analyzed &#8212; a sample from the frontal and oblique ramps (Figure 12). In general, the reverse faults and folds preserved in the epoxied samples from the frontal ramp accommodate transport to east, and those from the oblique ramp accommodate transport to the southeast. The strike-slip faults in all the samples accommodate dextral motion. This kinematic record along the frontal and oblique ramps supports previous models17-19, as well as the mesoscale fault data. These hand samples are novel way to analyze internal structures that may not be accessible in the field.

Watch this Scientific Journal Video about Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling at JoVE.com

Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling

Kinematic histories of fold-thrust belts are typically based on careful examinations of high-grade metamorphic rocks within a salient. We provide a novel method of understanding fold-thrust belts by examining salient-recess junctions. We analyze the oft-ignored upper crustal rocks using a combined approach of detailed fault analysis with experimental sandbox modeling.

Within fold-thrust belts, the junctions between salients and recesses may hold critical clues to the overall kinematic history. The deformation history ...

kinematic-history-salient-recess-junction-explored-through-combined

Nanyang Technological University

Research

JoVE Journal

Environment

8.2K Views.  Franklin and Marshall College. Kinematic histories of fold-thrust belts are typically based on careful examinations of high-grade metamorphic rocks within a salient. We provide a novel method of understanding fold-thrust belts by examining salient-recess junctions. We analyze the oft-ignored upper crustal rocks using a combined approach of detailed fault analysis with experimental sandbox modeling.

Video: Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling

Physiological, Morphological and Neurochemical Characterization of Neurons Modulated by Movement

The role of individual neurons and their function in neuronal circuits is fundamental to understanding the neuronal mechanisms of sensory and motor functions. Most investigations of sensorimotor mechanisms rely on either examination of neurons while an animal is static1,2 or record extracellular neuronal activity during a movement.3,4 While these studies have provided the fundamental background for sensorimotor function, they either do not evaluate functional information which occurs during a movement or are limited in their ability to fully characterize the anatomy, physiology and neurochemical phenotype of the neuron. A technique is shown here which allows extensive characterization of individual neurons during an in vivo movement. This technique can be used not only to study primary afferent neurons but also to characterize motoneurons and sensorimotor interneurons. Initially the response of a single neuron is recorded using electrophysiological methods during various movements of the mandible followed by determination of the receptive field for the neuron. A neuronal tracer is then intracellularly injected into the neuron and the brain is processed so that the neuron can be visualized with light, electron or confocal microscopy (Fig. 1). The detailed morphology of the characterized neuron is then reconstructed so that neuronal morphology can be correlated with the physiological response of the neuron (Figs. 2,3). In this communication important key details and tips for successful implementation of this technique are provided. Valuable additional information can be determined for the neuron under study by combining this method with other techniques. Retrograde neuronal labeling can be used to determine neurons with which the labeled neuron synapses; thus allowing detailed determination of neuronal circuitry. Immunocytochemistry can be combined with this method to examine neurotransmitters within the labeled neuron and to determine the chemical phenotypes of neurons with which the labeled neuron synapses. The labeled neuron can also be processed for electron microscopy to determine the ultrastructural features and microcircuitry of the labeled neuron. Overall this technique is a powerful method to thoroughly characterize neurons during in vivo movement thus allowing substantial insight into the role of the neuron in sensorimotor function.

A technique is described to quantify the in vivo physiological response of mammalian neurons during movement and correlate the physiology of the neuron with neuronal morphology, neurochemical phenotype and synaptic microcircuitry.

The role of individual neurons and their function in neuronal circuits is fundamental to understanding the neuronal mechanisms of sensory and motor ...

Neuroscience

Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With designs governed by the dynamic performance under human-induced loads, a strong demand exists for the verification and refinement of currently available load models. The present contribution uses a 3D inertial motion tracking technique for the characterization of the in-field pedestrian behavior. The technique is first tested in laboratory experiments with simultaneous registration of the corresponding ground reaction forces. The experiments include walking persons as well as rhythmical human activities such as jumping and bobbing. It is shown that the registered motion allows for the identification of the time variant pacing rate of the activity. Together with the weight of the person and the application of generalized force models available in literature, the identified time-variant pacing rate allows to characterize the human-induced loads. In addition, time synchronization among the wireless motion trackers allows identifying the synchronization rate among the participants. Subsequently, the technique is used on a real footbridge where both the motion of the persons and the induced structural vibrations are registered. It is shown how the characterized in-field pedestrian behavior can be applied to simulate the induced structural response. It is demonstrated that the in situ identified pacing rate and synchronization rate constitute an essential input for the simulation and verification of the human-induced loads. The main potential applications of the proposed methodology are the estimation of human-structure interaction phenomena and the development of suitable models for the correlation among pedestrians in real traffic conditions.

A protocol is presented for the characterization of the in-field pedestrian behavior and the simulation of the resulting structural response. Field-tests demonstrate that the in situ identified pacing rate and synchronization rate among the participants constitute an essential input for the simulation and verification of the human-induced loads.

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With ...

Engineering

Sit-to-stand-and-walk from 120% Knee Height: A Novel Approach to Assess Dynamic Postural Control Independent of Lead-limb

Individuals with sensorimotor pathology e.g., stroke have difficulty executing the common task of rising from sitting and initiating gait (sit-to-walk: STW). Thus, in clinical rehabilitation separation of sit-to-stand and gait initiation - termed sit-to-stand-and-walk (STSW) - is usual. However, a standardized STSW protocol with a clearly defined analytical approach suitable for pathological assessment has yet to be defined.
Hence, a goal-orientated protocol is defined that is suitable for healthy and compromised individuals by requiring the rising phase to be initiated from 120% knee height with a wide base of support independent of lead limb. Optical capture of three-dimensional (3D) segmental movement trajectories, and force platforms to yield two-dimensional (2D) center-of-pressure (COP) trajectories permit tracking of the horizontal distance between COP and whole-body-center-of-mass (BCOM), the decrease of which increases positional stability but is proposed to represent poor dynamic postural control.
BCOM-COP distance is expressed with and without normalization to subjects&#39; leg length. Whilst COP-BCOM distances vary through STSW, normalized data at the key movement events of seat-off and initial toe-off (TO1) during steps 1 and 2 have low intra and inter subject variability in 5 repeated trials performed by 10 young healthy individuals. Thus, comparing COP-BCOM distance at key events during performance of an STSW paradigm between patients with upper motor neuron injury, or other compromised patient groups, and normative data in young healthy individuals is a novel methodology for evaluation of dynamic postural stability.

Here, we present a novel protocol to measure positional stability at key events during the sit-to-stand-to-walk using the center-of-pressure to the whole-body-center-of-mass distance. This was derived from the force platform and three-dimensional motion-capture technology. The paradigm is reliable and can be utilized for the assessment of neurologically compromised individuals.

Individuals with sensorimotor pathology e.g., stroke have difficulty executing the common task of rising from sitting and initiating gait (sit-to-walk: ...

Behavior

Remote Magnetic Actuation of Micrometric Probes for in situ 3D Mapping of Bacterial Biofilm Physical Properties

Bacterial adhesion and growth on interfaces lead to the formation of three-dimensional heterogeneous structures so-called biofilms. The cells dwelling in these structures are held together by physical interactions mediated by a network of extracellular polymeric substances. Bacterial biofilms impact many human activities and the understanding of their properties is crucial for a better control of their development &#8212; maintenance or eradication &#8212; depending on their adverse or beneficial outcome. This paper describes a novel methodology aiming to measure in situ the local physical properties of the biofilm that had been, until now, examined only from a macroscopic and homogeneous material perspective. The experiment described here&#160;involves introducing magnetic particles into a growing biofilm to seed local probes that can be remotely actuated without disturbing the structural properties of the biofilm. Dedicated magnetic tweezers were developed to exert a defined force on each particle embedded in the biofilm. The setup is mounted on the stage of a microscope to enable the&#160;recording of time-lapse images of the particle-pulling period. The particle trajectories are then extracted from the pulling sequence and the local viscoelastic parameters are derived from each particle displacement curve, thereby providing the 3D-spatial distribution of the parameters. Gaining insights into the biofilm mechanical profile is essential from an engineer&#39;s point of view for biofilm control purposes but also from a fundamental perspective to clarify the relationship between the architectural properties and the specific biology of these structures.

Remote Magnetic Actuation of Micrometric Probes for in situ 3D Mapping of Bacterial Biofilm Physical Properties

This paper shows an original methodology based on the remote actuation of magnetic particles seeded in a bacterial biofilm and the development of dedicated magnetic tweezers to measure in situ the local mechanical properties of the complex living material built by micro-organisms at interfaces.

Bacterial adhesion and growth on interfaces lead to the formation of three-dimensional heterogeneous structures so-called biofilms. The cells dwelling in ...

Bioengineering

Measurement of Dynamic Scapular Kinematics Using an Acromion Marker Cluster to Minimize Skin Movement Artifact

The measurement of dynamic scapular kinematics is complex due to the sliding nature of the scapula beneath the skin surface. The aim of the study was to clearly describe the acromion marker cluster (AMC) method of determining scapular kinematics when using a passive marker motion capture system, with consideration for the sources of error which could affect the validity and reliability of measurements. The AMC method involves placing a cluster of markers over the posterior acromion, and through calibration of anatomical landmarks with respect to the marker cluster it is possible to obtain valid measurements of scapular kinematics. The reliability of the method was examined between two days in a group of 15 healthy individuals (aged 19-38 years, eight males) as they performed arm elevation, to 120&#176;, and lowering in the frontal, scapular and sagittal planes. Results showed that between-day reliability was good for upward scapular rotation (Coefficient of Multiple Correlation; CMC = 0.92) and posterior tilt (CMC = 0.70) but fair for internal rotation (CMC = 0.53) during the arm elevation phase. The waveform error was lower for upward rotation (2.7&#176; to 4.4&#176;) and posterior tilt (1.3&#176; to 2.8&#176;), compared to internal rotation (5.4&#176; to 7.3&#176;). The reliability during the lowering phase was comparable to results observed during the elevation phase. If the protocol outlined in this study is adhered to, the AMC provides a reliable measurement of upward rotation and posterior tilt during the elevation and lowering phases of arm movement.

This report presents details of how to adopt the acromion marker cluster method of obtaining scapular kinematics when using a passive marker motion capture device. As has been described in the literature, this method provides a robust, non-invasive, three-dimensional, dynamic and valid measurement of scapular kinematics, minimizing skin movement artifact.

The measurement of dynamic scapular kinematics is complex due to the sliding nature of the scapula beneath the skin surface. The aim of the study was to ...

Medicine

Subject-specific Musculoskeletal Model for Studying Bone Strain During Dynamic Motion

Bone stress injuries are common in sports and military trainings. Repetitive large ground impact forces during training could be the cause. It is essential to determine the effect of high ground impact forces on lower-body bone deformation to better understand the mechanisms of bone stress injuries. Conventional strain gauge measurement has been used to study in vivo tibia deformation. This method is associated with limitations including invasiveness of the procedure, involvement of few human subjects, and limited strain data from small bone surface areas. The current study intends to introduce a novel approach to study tibia bone strain under high impact loading conditions. A subject-specific musculoskeletal model was created to represent a healthy male (19 years, 80 kg, 1,800 mm). A flexible finite element tibia model was created based on a computed tomography (CT) scan of the subject&#39;s right tibia. Laboratory motion capture was performed to obtain kinematics and ground reaction forces of drop-landings from different heights (26, 39, 52 cm). Multibody dynamic computer simulations combined with a modal analysis of the flexible tibia were performed to quantify tibia strain during drop-landings. Calculated tibia strain data were in good agreement with previous in vivo studies. It is evident that this non-invasive approach can be applied to study tibia bone strain during high impact activities for a large cohort, which will lead to a better understanding of injury mechanism of tibia stress fractures.

During landing, lower-body bones experience large mechanical loads and are deformed. It is essential to measure bone deformation to better understand the mechanisms of bone stress injuries associated with impacts. A novel approach integrating subject-specific musculoskeletal modeling and finite element analysis is used to measure tibial strain during dynamic movements.

Bone stress injuries are common in sports and military trainings. Repetitive large ground impact forces during training could be the cause. It is ...

3D Kinematic Analysis for the Functional Evaluation in the Rat Model of Sciatic Nerve Crush Injury

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of sciatic nerve injury rodent models. In this protocol, we describe a novel kinematic analysis method that uses a three-dimensional (3D) motion capture apparatus for functional evaluations using a rat sciatic nerve crush injury model. First, the rat is familiarized with treadmill walking. Markers are then attached to the designated bone landmarks and the rat is made to walk on the treadmill at the desired speed. Meanwhile, the posterior limb movements of the rat are recorded using four cameras. Depending on the software used, marker tracings are created using both automatic and manual modes and the desired data are produced after subtle adjustments. This method of kinematic analysis, which uses a 3D motion capture apparatus, offers numerous advantages, including superior precision and accuracy. Many more parameters can be investigated during the comprehensive functional evaluations. This method has several shortcomings that require consideration: The system is expensive, can be complicated to operate, and may produce data deviations due to skin shifting. Nevertheless, kinematic analysis using a 3D motion capture apparatus is useful for performing functional anterior and posterior limb evaluations. In the future, this method may become increasingly useful for generating accurate assessments of various traumas and diseases.

We introduce a kinematic analysis method that uses a three-dimensional motion capture apparatus containing four cameras and data processing software for performing functional evaluations during fundamental research involving rodent models.

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of ...

Analysis of Expansion Patterns from SARPE Using Finite Element Models

Finite Element Analysis Model for Assessing Expansion Patterns from Surgically Assisted Rapid Palatal Expansion

Surgically assisted rapid palatal expansion (SARPE) was introduced to release bony resistance to facilitate skeletal expansion in skeletally mature patients. However, asymmetric expansion between the left and right sides has been reported in 7.52% of all SARPE patients, of which 12.90% had to undergo a second surgery for correction. The etiologies leading to asymmetric expansion remain unclear. Finite element analysis has been used to evaluate the stress associated with SARPE in the maxillofacial structures. However, as a collision of the bone at the LeFort I osteotomy sites occurs only after a certain amount of expansion, most of the existing models do not truly represent the force distribution, given that the expansion amount of these existing models rarely exceeds 1 mm. Therefore, there is a need to create a novel finite element model of SARPE that could perform a clinically required amount of expander activation for further analysis of the expansion patterns of the hemimaxillae in all three dimensions. A three-dimensional (3D) skull model from cone beam computed tomography (CBCT) was imported into Mimics and converted into mathematical entities to segment the maxillary complex, maxillary first premolars, and maxillary first molars. These structures were transferred into Geomagic for surface smoothing and cancellous bone and periodontal ligament creation. The right half of the maxillary complex was then retained and mirrored to create a perfectly symmetrical model in SolidWorks. A Haas expander was constructed and banded to the maxillary first premolars and first molars. Finite element analysis of various combinations of buccal osteotomies at different angles with 1 mm clearance was performed in Ansys. A convergence test was conducted until the desired amount of expansion on both sides (at least 6 mm in total) was achieved. This study lays the foundation for evaluating how buccal osteotomy angulation influences the expansion patterns of SARPE.

Author Spotlight: Development of a Novel Finite Element Analysis Model for Improved Orthognathic Surgical Techniques 

A set of novel finite element models of surgically assisted rapid palatal expansion (SARPE) that could perform a clinically required amount of expander activation with various angles of buccal osteotomy was created for further analysis of the expansion patterns of the hemimaxillae in all three dimensions.

Surgically assisted rapid palatal expansion (SARPE) was introduced to release bony resistance to facilitate skeletal expansion in skeletally mature ...

In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy

Several hip pathologies have been attributed to abnormal morphology with an underlying assumption of aberrant biomechanics. However, structure-function relationships at the joint level remain challenging to quantify due to difficulties in accurately measuring dynamic joint motion. The soft tissue artifact errors inherent in optical skin marker motion capture are exacerbated by the depth of the hip joint within the body and the large mass of soft tissue surrounding the joint. Thus, the complex relationship between bone shape and hip joint kinematics is more difficult to study accurately than in other joints. Herein, a protocol incorporating computed tomography (CT) arthrography, three-dimensional (3D) reconstruction of volumetric images, dual fluoroscopy, and optical motion capture to accurately measure the dynamic motion of the hip joint is presented. The technical and clinical studies that have applied dual fluoroscopy to study form-function relationships of the hip using this protocol are summarized, and the specific steps and future considerations for data acquisition, processing, and analysis are described.

In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy

Dual fluoroscopy accurately captures in vivo dynamic motion of human joints, which can be visualized relative to reconstructed anatomy (e.g., arthrokinematics). Herein, a detailed protocol to quantify hip arthrokinematics during weight-bearing activities of daily living is presented, including the integration of dual fluoroscopy with traditional skin marker motion capture.

Several hip pathologies have been attributed to abnormal morphology with an underlying assumption of aberrant biomechanics. However, structure-function ...

Assessing a Functional Neuromuscular Junction Via Simultaneous Optical Stimulation and Video Recording

Source:&#160; Liberman, M., et al., <a href="https://app-jove-com.remotexs.ntu.edu.sg/v/63759">Engineering and Characterization of an Optogenetic Model of the Human Neuromuscular Junction.</a> J. Vis. Exp. (2022).
This video demonstrates a method to assess functional neuromuscular junctions. Using a bioreactor containing muscle tissue and motor neurons, along with fluorescent microscopy, the light-sensitive channels in the neurons are stimulated to generate electrical signals, causing muscle fiber contractions.

All procedures involving sample collection have been performed in accordance with the institute&#39;s IRB guidelines.
1. Bioreactor preparation

	Make ...

Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling

Samenvatting

Meer video's verkennen