Ostler Fault Research Articles

Not all faults are conductive: the effects of seasonal weather changes on the near‐surface expression of faults

ABSTRACTThe near‐surface electrical properties of faults can change with seasonal climate, depending on the nature of the materials filling the faults, e.g. fault gouge vs fractured rock, and be subject to seasonal weather changes. A period of dry weather, especially in a hot climate, can dry out the near‐surface sections of faults that are filled with porous materials, thus increasing the electrical resistivity, yet may not affect a fault that is filled with fine‐grained material that retains moisture well. Conversely, a sustained period of wet weather can fill porous faults with water, thus decreasing the resistivity. To illustrate the impact of seasonal weather changes on the near‐surface properties of faults, we conducted electrical imaging and ground‐penetrating radar surveys during the late spring, summer, and early autumn on the Glen Lyon and Benmore segments of the Ostler Fault, respectively, in the South Canterbury and Central Otago provinces of the South Island of New Zealand. The changes in the response are clear: seasonal weather changes can affect the near‐surface properties of faults, and the geophysical responses from the near‐surface faults can vary depending on the nature of the material filling the fault.

Palaeoseismic constraints on Holocene surface ruptures along the Ostler Fault, southern New Zealand

Palaeoseismic trenching along the central Ostler fault zone reveals the nature and timing of past surface-rupturing earthquakes. A 26 m long trench excavated into a last-glacial (26.5 ka) outwash surface cut by the Ruataniwha strand of the North Central Ostler fault reveals evidence for at least two metre-scale surface displacements in the last c. 8 ka. Detailed logging of colluvial wedge and alluvial stratigraphy, combined with optically stimulated luminescence dating of loess within colluvial packages, provides a maximum bound on the most recent earthquake (MRE) of 2.3–4.5 ka. The MRE resulted in a surface displacement of at least 1.8 m, consistent with an estimated moment magnitude (M) 6.9–7.1 earthquake based on the total 60 km length of the Ostler fault zone. The penultimate event occurred sometime before 4.1–8.4 ka and resulted in a comparable or larger surface displacement. Similar ages from samples collected in previous trenches on the Ostler fault suggest that surface ruptures may persist across kilometre-scale stepovers defined by the active surface trace of the fault. At the trench scale, comparison between dip slip calculated from topographic fault-scarp profiling (7.8 m) and the total offset of exposed outwash gravels (6.0 m) suggests that surface folding immediately adjacent to the fault scarp accommodates roughly 25% of the total slip. Given a previously reported recurrence interval of c. 2–5 ka for the Ostler fault, the presence of only 2–3 palaeoearthquakes on the 26.5 ka outwash surface indicates that additional events likely occurred on nearby fault scarps in an overall complex zone of surface faulting.

Structure and evolution of the seismically active Ostler Fault Zone (New Zealand) based on interpretations of multiple high resolution seismic reflection profiles

To improve our understanding of active faulting away from the main plate boundary on New Zealand's South Island, we have acquired high resolution seismic data across the Ostler Fault Zone Twelve 1.2 km long lines perpendicular to fault strike and a 1.6 km long crossline were collected in a region of the MacKenzie Basin where surface mapping delineates significant complexity in the form of two non-overlapping reverse fault strands separated by a transfer zone characterised by multiple smaller strands and increased folding. Interpretation of the resultant images includes a 45–55° west-dipping principal fault and two 25–30° west-dipping subsidiary faults, one in the hanging wall and one in the footwall of the principal fault. The geologically mapped complexities are shown to be caused by shallow variations in the structure of the principal fault, which breaks the surface in the north and south but not within the transfer zone, where it forms a triangle zone with associated backthrusting and minor faulting. These complexities only extend to ~ 300 m depth. Structures below this level are markedly simpler and much more 2D in nature, with the principal fault strand extending over a much longer distance than the individual strands observed at the surface. Since longer faults are susceptible to larger earthquakes than shorter ones, seismic hazard at the study site may be higher than previously thought. Multiple surface fault strands that give way to a single more major stand at relatively shallow depths may be a common feature of segmented fault systems. The deepest layered reflections at our site are consistent with the presence of a Late Cretaceous (?)–Tertiary basin underlying the present-day MacKenzie Basin. Structural restoration of the seismic images back to the base of Quaternary fluvioglacial terraces and back to the top of a Late Pliocene–Pleistocene fluviolacustrine unit indicate that compression was initiated prior to the Late Pliocene and that it has continued at a comparatively steady rate of about a millimetre per year to the present day. The fluviolacustrine unit has experienced 440–800 m of along-fault vertical offset and 870–1080 m of horizontal shortening since that time. Our study demonstrates that structural reconstructions based on high resolution seismic reflection data provide critical displacement information that can be used to estimate slip rates.

Along-strike growth of the Ostler fault, New Zealand: Consequences for drainage deflection above active thrusts

[1] Rarely are geologic records available to constrain the spatial and temporal evolution of thrust-fault growth as slip accumulates during repeated earthquake events. Here, we utilize multiple generations of dated and deformed fluvial terraces to explore two key aspects of the along-strike kinematic development of the Ostler fault zone in southern New Zealand over the past ∼100 k.y.: accumulation of fault slip through space and time and fixed-length thrust growth that results in patterns of drainage diversion suggestive of laterally propagating faults. Along the Ostler fault, surface deformation patterns revealed by topographic surveying of terrace profiles in nine transverse drainages define systematic variations in fault geometry and suggest deformation over both listric and planar thrust ramps. Kinematic modeling of folded terrace profiles and >100 fault-scarp surveys along major fault sections reveals remarkably similar slip distributions for multiple successions of geomorphic surfaces spanning ∼100 k.y. Spatially abrupt and temporally sustained displacement gradients across zones of fault section overlap suggest that either persistent barriers to fault propagation or interference between overlapping faults dominate the interactions of fault tips from the scale of individual scarps to the entire fault zone. Deformed terrace surfaces dated using optically stimulated luminescence and cosmogenic radionuclides indicate steady, maximum rates of fault slip of ∼1.9 mm/yr during the Late Quaternary. Slip data synthesized along the central Ostler fault zone imply that displacement accumulated at approximately constant fault lengths over the past ∼100 k.y. A northward temporal progression of abandoned wind gaps along this section thus reflects lateral tilting in response to amplification of displacement, rather than simple fault lengthening or lateral propagation. Oscillations of climate at ∼104-yr time scales modulate the formation and incision of geomorphic surfaces during successive glacial stages. Superimposed on apparently steadier rates of fault slip, such climate-dependent surfaces contribute to a pattern of progressive drainage deflection along the central Ostler fault zone that is largely independent of fault propagation.

Three-dimensional GPR imaging of the Benmore anticline and step-over of the Ostler Fault, South Island, New Zealand

SUMMARY Because surface processes can frequently remove, mask or suppress the surface expression of faults, geophysical imaging is needed to provide information on the geometric expression of the fault in the subsurface, including dips, the presence or absence of splays and folds and the nature of the material in the fault plane. Subsurface data become especially important where a step-over occurs, however the mechanism of the step-over is not clear. The Ostler Fault is a major thrust fault in the Mackenzie Basin of the South Island of New Zealand. The geometry of the fault changes along its length, with a number of growing anticlines and step-overs forming the Ostler Fault Zone (OFZ). One of these anticlines occurs along the Benmore segment of the OFZ. A three-dimensional (3-D) ground penetrating radar (GPR) survey was carried out to supplement detailed surface topographic mapping and help characterize the nature of the OFZ at Benmore. To cover the 1 km length of the step-over, the 3-D survey was done with a coarse yet regular 50 m line spacing. The individual fault splays were continuous and could be traced from line to line. Not all splays had surface expression, whereas almost all surface features had corresponding subsurface expression. As the fault approaches the anticline and multiple splays become apparent, the main fault simply develops into one of a set of splays as the deformation becomes distributed across the wider zone. Eventually, one of the other splays becomes the primary fault strand, and the others are abandoned.

Processing and preliminary interpretation of noisy high-resolution seismic reflection/refraction data across the active Ostler Fault zone, South Island, New Zealand

Abstract In an attempt to understand the structure of active faults as they emerge from bedrock into shallow semi-consolidated and unconsolidated sediments, we have recorded a comprehensive high-resolution seismic reflection/refraction data set across the Ostler Fault zone on the central South Island of New Zealand. This fault zone, which absorbs 1–2 mm/yr of compression associated with oblique convergence of the Pacific and Australian tectonic plates, consists of a series of surface-rupturing N–S trending, west-dipping reverse faults that offset a thick sequence of Quaternary glacial outwash and late Neogene fluvio-lacustrine sediments of the Mackenzie Basin. Our study focuses on a region of the basin where two non-overlapping fault segments are separated by a transfer zone. Deformation in this area is accommodated by offsets on multiple small faults and by folding in their hanging walls. The seismic data with source and receiver spacing of 6 and 3 m and nominal CMP fold of 60 was acquired along twelve 1.2 km long lines orthogonal to fault strike and an additional 1.6 km long tie-line parallel to fault strike. The combination of active deformation and shallow glacial outwash sediments results in particularly complicated seismic data, such that application of relatively standard processing schemes yields only poor quality images. We have designed a pre- and post-stack reflection/refraction processing scheme that focuses on minimising random and source-generated noise, determining appropriate static corrections and resolving contrasting reflection dips. Application of this processing scheme to the Ostler Fault data provides critical information on fault geometry and offset and on sedimentary structures from the surface to ∼ 800 m depth. Our preliminary interpretation of one of the lines includes complex deformation structures with folding and multiple subsidiary fault splays on either side of a ∼ 50° west-dipping primary fault plane.

Characterization of the shallow structures of active fault zones using 3‐D ground‐penetrating radar data

Where they can be correlated with geological exposures and trenches, 3‐D ground‐penetrating radar (GPR) data can contribute critical subsurface information to paleoseismic investigations. Because active faults are typically characterized by complicated near‐surface structures that vary with the styles of faulting and the types of rock that are ruptured, GPR data can be difficult to interpret. We have acquired 3‐D GPR data sets across three active fault zones within New Zealand that have different deformation styles: the strike‐slip Wellington fault zone, reverse faults of the Ostler fault zone, and normal faults of the Maleme fault zone. To improve our interpretation of the processed GPR volumes, we employed two suites of geometric attributes. The first suite was computed using a coherence‐based algorithm. It provided estimates of the coherency, azimuth, and dip of reflections. The second suite quantified the volumetric textures of reflections, which allowed different reflection facies to be defined objectively. We have demonstrated how some attributes were more successful at visualizing certain structural or depositional characteristics than others. For example, the coherency attribute was an excellent tool for highlighting normal faults within volcanic deposits of the Maleme fault zone, whereas the texture‐based attributes were most useful for discriminating between the gravel and metasediment units juxtaposed by the Wellington fault zone. Our GPR data sets and associated attribute volumes showed details of near‐surface fault geometry that were not obvious from surface mapping, and they revealed evidence of off‐fault deformation, gravitational collapse, and topple structures.

Surface breakthrough of a basement fault by repeated seismic slip episodes: The Ostler Fault, South Island, New Zealand

The Ostler Fault is one of the major active reverse faults in the piedmont of the Southern Alps, SE of the Alpine Fault. We present a new geological and morphotectonic map of the southern Ostler Fault, integrated with two seismic reflection profiles across the active central segments of the fault. Segmented, subparallel scarps define a N‐S belt (∼40 km long and 2−3 km wide) of pure reverse faults, which upthrow and back‐tilt a panel of Plio‐Pleistocene terrestrial units (2.4−1.0 Ma) plus the overlying glacial outwash (<200 ka). Uplift gradients, the chronology of newly faulted markers, and tectonically controlled diversion of paleodrainages, all indicate progressive S to N breakthrough of the surface trace of the Ostler Fault in the last 2.4 Ma. The new seismic data define a main fault segment dipping 50°−60°W to depths of ∼1.5 km, with a vertical throw of 800 m, and a shortening of ∼30%. The fault geometry and kinematics and the subsurface data favor the interpretation that the Ostler Fault propagated updip across the Plio‐Quaternary terrestrial sequence as the emerging, high‐angle splay of an inherited Late Cretaceous−Paleocene normal fault, that underwent repeated cycles of compressional reactivation in the last 2.4 Ma.

Channel width response to differential uplift

The role of channel width and slope adjustments to differential uplift in rivers within actively deforming terrains remains contentious. Here high‐resolution topographic surveying of formerly antecedent outwash channels demonstrates marked changes in channel width as a primary response to differential uplift. For five Late Quaternary alluvial paleochannels crossing small folds along the active Ostler fault zone of southern New Zealand, nearly continuous measurements of paleochannel width and concomitant incision reveal abrupt narrowing of widths toward minimum values at channel positions coincident with the initial uplift. When the magnitude of differential uplift is sufficiently small, narrowing alone permits these channels to remain antecedent. In the context of a unit stream power model for fluvial erosion, observed limits on the magnitude of channel narrowing suggest that above some threshold amount of differential uplift, continued incision requires concomitant changes in channel gradient. Thus when crossing small growing folds, alluvial rivers simply narrow their channels, whereas larger folds that demand greater incision prompt an initial narrowing followed by channel steepening.

Geomorphic constraints on listric thrust faulting: Implications for active deformation in the Mackenzie Basin, South Island, New Zealand

Deformed fluvial terraces preserved over active thrust‐related folds record the kinematics of folding as fault slip accumulates on the underlying thrust. In the Mackenzie Basin of southern New Zealand, the kinematics revealed by folded fluvial terraces along the active Ostler and Irishman Creek fault zones are inconsistent with traditional models for thrust‐related folding in which spatially uniform rock uplift typically occurs over planar fault ramps. Instead, warped and tilted terraces in the Mackenzie are characterized by broad, continuous backlimbs and abrupt forelimbs and suggest folding through progressive limb rotation. By relating this pattern of surface deformation to the underlying thrust with a newly developed, simple geometric and kinematic model, we interpret both faults as listric thrusts rooted at depth into gently dipping planar fault ramps. Constraints on the model from detailed topographic surveying of deformed terraces, ground‐penetrating radar over active fault scarps, and luminescence dating of terrace surfaces suggest slip rates for the Ostler and Irishman Creek faults of ∼1.1–1.7 mm/yr and ∼0.5–0.7 mm/yr, respectively. The predicted depth of listric faulting for the Ostler fault (0.7−0.2+0.1km) and the Irishman Creek fault (1.3−0.5+0.1km) generally agrees with geophysical estimates of basin depth in the Mackenzie and suggests control of preexisting basin architecture on the geometry of active thrusting. Despite the potential effects of changes in fault curvature and hanging wall internal deformation, the methodology presented here provides a simple tool for approximating the kinematics of surface deformation associated with slip along listric, or curviplanar, thrust faults.

Thrust-fault growth and segment linkage in the active Ostler fault zone, New Zealand

Thrust faulting is a fundamental mode of crustal deformation, yet many of the key geometrical attributes of thrust faults and the controls on fault rupture, growth, and linkage remain poorly resolved. Numerous surface-rupturing thrust faults cut through upper Quaternary glacial outwash terraces within the Ostler Fault zone, an active thrust system in the Southern Alps, New Zealand. We use these deformed marker surfaces to define the three-dimensional deformation field associated with their surface expression and to map displacement and length on ∼40 fault segments. Displacement transfer across two fault segment arrays occurs in distinctly different styles. In one, displacement is transferred between en échelon fault segments to produce a smooth, linear displacement gradient. In the other, large-scale folding and a population of small faults transfer displacement between two non-overlapping fault segments, with a residual displacement minimum within the transfer zone. Size distribution of fault-segment length and maximum displacement follow a power-law scaling relationship. Maximum displacement ( D max) scales linearly with and represents ∼1% of segment trace length ( L). D max/ L data from the segments of the Ostler Fault zone display similar scaling to a global fault dataset. This similarity is surprising, given that the observed displacements along the Ostler Fault represent only 20 ky of slip on fault segments that are likely to be many times older.

Long-term changes to river regimes prior to late Holocene coseismic faulting, Canterbury, New Zealand

Two sites are described from range front faults along the foothills of the Southern Alps of New Zealand, where apparently a period of 200–300 years of accelerated river incision preceded late Holocene coseismic ruptures, each probably in excess of M w 7.5. They relate to separate fault segments and seismic events on a transpressive system associated with fault-driven folding, but both show similar evidence of off-plane aseismic deformation during the downcutting phase. The incision history is documented by the ages, relative elevations and profiles of degradation terraces. The surface dating is largely based on the weathering rind technique of McSaveney (McSaveney, M.J., 1992. A Manual for Weathering-rind Dating of Grey Sandstones of the Torlesse Supergroup, New Zealand. 92/4, Institute of Geological and Nuclear Sciences), supported by some consistent radiocarbon ages. On the Porters Pass Fault, drainage from Red Lakes has incised up to 12 m into late Pleistocene recessional outwash, but the oldest degradation terrace surface T I is dated at only 690±50 years BP. The upper terraces T I and T II converge uniformly downstream right across the fault trace, but by T III the terrace has a reversed gradient upstream. T II and T III break into multiple small terraces on the hanging wall only, close to the fault trace. Continued backtilting during incision caused T IV to diverge downstream relative to the older surfaces. Coseismic faulting displaced T V and all the older terraces by a metre high reverse scarp and an uncertain right lateral component. This event cannot be younger than a nearby ca. 500 year old rock avalanche covering the trace. The second site in the middle reaches of the Waipara River valley involves the interaction of four faults associated with the Doctors Anticline. The main river and tributaries have incised steeply into a 2000 year old mid-Holocene, broad, degradation surface downcutting as much as 55 m. Beginning approximately 600 years ago accelerating incision eventually attained rates in excess of 100 mm/year in those reaches closely associated with the Doctors Anticline and related thrust and transfer faults. All four faults ruptured, either synchronously or sequentially, between 250 and 400 years ago when the river was close to 8 m above its present bed. Better cross-method checks on dating would eliminate some uncertainties, but the apparent similarities suggest a pattern of precursor events initiated by a period of base level drop extending for several kilometres across the structure, presumably in response to general uplift. Over time, deformation is concentrated close to the fault zone causing tilting of degradation terraces, and demonstrably in the Waipara case at least, coseismic rupture is preceded by marked acceleration of the downcutting rate. Overall base level drop is an order of magnitude greater than the throw on the eventual fault scarp. The Ostler Fault (Van Dissen et al., 1993) demonstrates that current deformation is taking place on similar thrust–fault driven folding in the Southern Alps. Regular re-levelling since 1966 has shown uplift rates of 1.0–1.5 mm/year at the crest of a 1–2 km half wave length anticline, but this case also illustrates the general problem of interpreting the significance of rates derived from geophysical monitoring relative to the long term seismic cycle. If the geomorphic signals described can be shown to hold for other examples, then criteria for targeting faults approaching the end of the seismic cycle in some tectonic settings may be possible.

Tectonic hydrothermal gold mineralisation in the outboard zone of the Southern Alps, New Zealand

Abstract Gold‐bearing veins cut a belt of low‐grade (pumpellyite‐actinolite/greenschist facies) schist in the Ben Ohau Range to the east of the Main Divide, in the outboard zone of the Southern Alps continental collisional zone, New Zealand. The schist has been exposed along the currently active Ostler Fault system, which has had c. 5 km of reverse motion since the Pliocene. The veins consist of quartz, ankerite, calcite, chlorite, and pyrite, with minor chalcopyrite and galena. Hydrothermal chlorite contains about 490 ppm Zn, and the gold contains 3–5 wt% Ag. Hydrothermal alteration of host rock is minor apart from Sr enrichment (up to four times background). Fluid inclusions in quartz are aqueous with minor dissolved CO2 and salts (<4 wt% NaCl equivalent), and homogenise at 236–270°C. The veins formed at 300 ± 20°C and 1000 ± 800 bars fluid pressure, probably under a hydrostatic fluid pressure regime. Oxygen and carbon isotopic data (δ18O = +10 to +14; δ13C = ‐6 to ‐10‰) are similar to data from economic metamorphogenic Au deposits of the nearby Otago Schist, but minor meteoric incursion may have occurred. Isotopic data are also similar to veins formed in the inboard zone of the Southern Alps orogen. The Ben Ohau veins demonstrate that gold can be concentrated in low‐grade schists distant from the most active part of the hydrothermal system driven by continental collision.

Deformation monitoring of the ostler fault zone, South Island, New Zealand

The Ostler Fault Zone is a zone of Quaternary reverse faulting along the western margin of the Mackenzie Basin, South Island, New Zealand. During investigations for and construction of the Ohau-A Power Project, a number of survey patterns were designed and installed to monitor ground deformation in the area of the fault zone. A triangulation network, two long and two short levelling routes, and six tilt levelling patterns have been installed at various times since 1964. Analysis of the levelling data shows that vertical deformation has occurred within the ault zone at a near constant rate for the last 20 years. Deformation consists of buckling about fault traces at a maximum rate of uplift of approximately 1 mm/yr. The vertical deformation preserved over 16,000–25,000 yrs has a similar rate although it is dominated by displacement across the fault zone as a whole. Analysis of triangulation data spanning up to 100 years indicates that significant horizontal strain is occurring, with the axis of relative contraction approximately perpendicular to the trend of the fault.

Advances in microminiaturization : M. F. Wolff, Electronics, Feb. 15, 1963, p. 45

To improve our understanding of active faulting away from the main plate boundary on New Zealand's South Island, we have acquired high resolution seismic data across the Ostler Fault Zone Twelve 1.2 km long lines perpendicular to fault strike and a 1.6 km long crossline were collected in a region of the MacKenzie Basin where surface mapping delineates significant complexity in the form of two non-overlapping reverse fault strands separated by a transfer zone characterised by multiple smaller strands and increased folding. Interpretation of the resultant images includes a 45–55° west-dipping principal fault and two 25–30° west-dipping subsidiary faults, one in the hanging wall and one in the footwall of the principal fault. The geologically mapped complexities are shown to be caused by shallow variations in the structure of the principal fault, which breaks the surface in the north and south but not within the transfer zone, where it forms a triangle zone with associated backthrusting and minor faulting. These complexities only extend to ~ 300 m depth. Structures below this level are markedly simpler and much more 2D in nature, with the principal fault strand extending over a much longer distance than the individual strands observed at the surface. Since longer faults are susceptible to larger earthquakes than shorter ones, seismic hazard at the study site may be higher than previously thought. Multiple surface fault strands that give way to a single more major stand at relatively shallow depths may be a common feature of segmented fault systems.The deepest layered reflections at our site are consistent with the presence of a Late Cretaceous (?)–Tertiary basin underlying the present-day MacKenzie Basin. Structural restoration of the seismic images back to the base of Quaternary fluvioglacial terraces and back to the top of a Late Pliocene–Pleistocene fluviolacustrine unit indicate that compression was initiated prior to the Late Pliocene and that it has continued at a comparatively steady rate of about a millimetre per year to the present day. The fluviolacustrine unit has experienced 440–800 m of along-fault vertical offset and 870–1080 m of horizontal shortening since that time. Our study demonstrates that structural reconstructions based on high resolution seismic reflection data provide critical displacement information that can be used to estimate slip rates.

Microelectronics, Part II : W. O. Hamlin, Semiconductor Products, Dec. 1962, p. 29

To improve our understanding of active faulting away from the main plate boundary on New Zealand's South Island, we have acquired high resolution seismic data across the Ostler Fault Zone Twelve 1.2 km long lines perpendicular to fault strike and a 1.6 km long crossline were collected in a region of the MacKenzie Basin where surface mapping delineates significant complexity in the form of two non-overlapping reverse fault strands separated by a transfer zone characterised by multiple smaller strands and increased folding. Interpretation of the resultant images includes a 45–55° west-dipping principal fault and two 25–30° west-dipping subsidiary faults, one in the hanging wall and one in the footwall of the principal fault. The geologically mapped complexities are shown to be caused by shallow variations in the structure of the principal fault, which breaks the surface in the north and south but not within the transfer zone, where it forms a triangle zone with associated backthrusting and minor faulting. These complexities only extend to ~ 300 m depth. Structures below this level are markedly simpler and much more 2D in nature, with the principal fault strand extending over a much longer distance than the individual strands observed at the surface. Since longer faults are susceptible to larger earthquakes than shorter ones, seismic hazard at the study site may be higher than previously thought. Multiple surface fault strands that give way to a single more major stand at relatively shallow depths may be a common feature of segmented fault systems.The deepest layered reflections at our site are consistent with the presence of a Late Cretaceous (?)–Tertiary basin underlying the present-day MacKenzie Basin. Structural restoration of the seismic images back to the base of Quaternary fluvioglacial terraces and back to the top of a Late Pliocene–Pleistocene fluviolacustrine unit indicate that compression was initiated prior to the Late Pliocene and that it has continued at a comparatively steady rate of about a millimetre per year to the present day. The fluviolacustrine unit has experienced 440–800 m of along-fault vertical offset and 870–1080 m of horizontal shortening since that time. Our study demonstrates that structural reconstructions based on high resolution seismic reflection data provide critical displacement information that can be used to estimate slip rates.