Abstract. Betsie Hopper a and Brendan Duffy b a Colorado College, b Department of Geology, University of Canterbury

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1 New Lidar data reveals slip transfer from the Hope Fault to the Kaikoura Fault Key Terms (Hope Fault, Lidar, Horst-Graben, Jordan Thrust, Kaikoura Fault) Betsie Hopper a and Brendan Duffy b a Colorado College, b Department of Geology, University of Canterbury Abstract Examining Lidar of the Kaikoura Peninsula reveals a previously unknown fault trace projecting off the Hope Fault: a Horst-Graben structure strikes eastward from the division between the Mt. Fyffe and Seaward sections of the Hope Fault. This location is significant since mm of slip is partitioned off of the Hope Fault between the Mt. Fyffe and Seaward sections. Lidar measurements and GPR survey data reveals that this trace records a maximum vertical offset of 2m, as well as a series of shorter, younger scarps that are all offset by multiples of 0.4m. Schmidt Hammer data from an abandoned, faulted streambed indicates a surface age of 3700 ± 800 yrs. Using the age and offset data, a vertical slip rate of 0.05 mm/yr was estimated. Based on the vertical slip rate, the Horst Graben has a probable extension rate of 0.06 mm/yr, although rates of up to 0.24 mm/yr are plausible. The presence of this Horst-Graben shows extension is occurring on the southern side of the Hope Fault, suggesting that a portion of the slip from the Hope fault is being transferred to the offshore Kaikoura Fault. Previously, it has been assumed that all of the decrease in slip along the Hope Fault is absorbed by the Jordan Thrust. This paper outlines how the new Horst-Graben feature was measured and dated, as well as how slip and extension was calculated. In doing so, it lays the foundation for re-analysis of slip distribution and associated hazards along the Hope Fault- Jordan Thrust section of the Marlborough Fault system. 30

2 Introduction Significance of the Problem New Zealand sits on the plate boundary of the Pacific and Australian plates, with the Australian plate converging on the Pacific plate at a rate of about 46 ±3 mm/yr. 1 On the South Island, most of this plate boundary motion is taken up by the Alpine Fault, which runs from the south end of the island to Lake Brunner. At this point, the stress is distributed across the Marlborough Fault System, a fan of NE- SW striking faults, as shown by Figure 1. 2 It is vital to understand the risk posed by the South Island s network of major faults. The most recent hazard assessment of the Alpine Fault and Marlborough Fault system uses slip rate, along with several other variables, to calculate maximum earthquake magnitudes for the major faults. 3 Based on the presence of a newly-discovered Horst-Graben structure, this paper suggests that slip could be distributed differently than previously assumed along several major features. It is important to determine if it is necessary to re-assess slip distribution along the Hope Fault, Jordan Thrust, and Kaikoura fault, as that could impact earthquake magnitude and risk calculations for the Kaikoura area. These features are shown in Figure 2, within the spatial context of our study site. Decrease in Slip along the Hope Fault Within the Marlborough fault system, the Hope Fault has the highest Holocene slip rate, accommodating around 70% of the slip from the Alpine Fault. 4 Estimates of slip vary along the main trace of the Hope Fault, ranging from 15mm/yr to 42mm/yr. 5 This study assumes an average slip rate of 20 to 25 mm/year along the Hope Fault, and a minimum rate of 16±5 mm/year of slip at the northernmost part of the Mt. Fyffe Section. 6 Along the northeastern-most 10 km of the Hope fault, known as the Seaward Segment, slip estimates are significantly lower. Estimates range from 2mm/yr to 7.5mm/year. 7 As the Seaward segment continues offshore, there are very few detectable traces, 1 (Van Dissen & Yeats, 1991) 2 (Van Dissen & Yeats, 1991) 3 (Investigations and Monitoring Group, Environment Canterbury, 2007) 4 (Langridge, et al., 2010) (Van Dissen & Yeats, 1991) 5 (Coulter, 2007) (Cowan, 1989) (Knuepfer, 1984) (Knuepfer, 1988) (Knuepfer, 1992); (Langridge & Berryman, 2005), (Langridge, et al., 2003). For more detailed information on Hope Fault slip rates, see Appendix A: Table 1 6 (Coulter, 2007) (Van Dissen R., 1989) (Van Dissen & Yeats, 1991). For further information see Appendix A: Table 1 and Figure 7 7 (Coulter, 2007) (Knuepfer, 1984) (Van Dissen R., 1989);. For further information, Appendix A: Table 1 and Figure 7

3 further indicating that the Seaward section of the Hope fault has a significantly smaller slip rate. 8 Based on previous studies, a slip rate of 4 ±2 mm/yr is assumed for the Seaward Segment. The significant drop in slip rate indicates that at the boundary between the Mt. Fyffe section and the Seaward section, slip is being partitioned off the Hope Fault. 9 Using the slip rate from the Mt. Fyffe Section gives a minimum decrease in slip of 12 ±5mm/yr, while using the average slip for the entire fault suggests that 18.5 ±5.5 mm/yr of slip are being lost. Based on these slip differentials, this study assumes that mm/yr of slip is diverted onto some other feature or features at the junction of the Mt. Fyffe and Seaward sections of the Hope fault. The Jordan Thrust and Uplift of the Seaward Kaikoura Range Current theory posits that all of the slip that disappears from the Hope Fault is absorbed by the Jordan Thrust. Van Dissen and Yeats suggest that the Jordan Thrust, which curves northward from the Hope fault at the junction of the Mt. Fyffe and Seaward segments of the Hope fault, acts as a restraining bend where thrust faulting causes uplift on the inland side of the fault. 10 This uplift has created the Seaward Kaikoura Range, as seen in Figure 3. It has been established that the other major faults in the area, the Kowhai and Fyffe Faults, have small enough slip rates any slip partitioned onto those two features is negligible. 11 Given the change in slip rates on the Hope Fault, the Jordan Thrust is absorbing anywhere from 12 ±5mm/yr to 18.5 ±5.5 mm/yr of slip. According to Van Dissen and Yeats s calculations, if 15 to 20 mm/year of slip is absorbed by the mountains at the 35 degree angle dip of the Jordan thrust, the range should be uplifted at a rate of 7 to 10 mm/yr. 12 Independent estimates of the uplift of the Seaward Kaikoura range are up to 10mm/yr and 6 to 10mm/yr. 13 This indicates that it is possible for the Jordan Thrust to accommodate all of the slip that is partitioned off the Hope Fault, but only if mountainbuilding in the Kaikoura Range occurs close to the maximum possible rate. Further, the Jordan thrust is completely blind, making it difficult to be certain of a 35 degree dip at depth. 14 Although it is clear that the Jordan Thrust absorbs a large amount of slip, there is a significant amount of uncertainty surrounding the actual quantity of slip that is absorbed. 8 (Coulter, 2007) 9 (Van Dissen & Yeats, 1991) 10 (Van Dissen & Yeats, 1991) 11 (Van Dissen & Yeats, 1991) 12 (Van Dissen & Yeats, 1991) 13 (Van Dissen & Yeats, 1991) 14 (Van Dissen & Yeats, 1991)

4 Extension and transfer of Slip to the Kaikoura Fault New Lidar data suggests that the Jordan Thrust does not accommodate all of the slip that is partitioned off the Hope Fault. Lidar images reveal a pair of scarps less than 2km away from the Mt. Fyffe section of the Hope Fault. These slopes face away from each other, creating a Horst-Graben structure running NE to SW. The presence of a Horst-Graben feature indicates extension along the Mt. Fyffe section of the Hope Fault. Extension increases the relative southward movement of the block of land east of the Horst-Graben and south of the Hope Fault. This movement corresponds with the relative motion of Kaikoura fault, an offshore right lateral fault that runs parallel to the Hope Fault. 15 The recognition of a Horst-Graben structure south of the Hope Fault is significant because it suggests an alternative to the theory that the Jordan Thrust is absorbing all of the slip lost along the Hope Fault. Instead, some of the slip has been transferred to the Kaikoura fault through extension, although a significant portion still feeds into the Jordan Thrust. Calculating the extension rate of the newly identified Horst-Graben is first step towards proving an extension-based alternative hypothesis. This study finds vertical offset, calculates a surface age, calculates slip rate, and estimates extension for the Horst Graben. By doing so, it refines the current theory on distribution of slip along the Hope Fault, Kaikoura Fault, and Jordan Thrust. It also lays the groundwork for future research, thereby enhancing our understanding of the southeast section of the Marlborough Fault System. Geologic Setting Study Site The Horst-Graben defined in this paper is located about 10km northeast of the Kaikoura Peninsula. The Mt. Fyffe section of the Hope Fault borders the study area to the north, and the Hapuku River defines its eastern edge. Horst-Graben Feature runs roughly NE to SW, as shown in Figure 4. The two scarps run across a series of three paddocks bordered by drainage ditches. The drainage ditches have been used to divide the north-facing scarp into three sections. An abandoned, slightly offset stream channel also cuts across the North Facing scarp, between Section1 and Section2 of the scarp. Schmidt hammer data was collected from an area about 100m away from the fault, within the same paddock as Section2 of the N-Facing scarp. 15 (Barnes & Audru, 1999)

5 Stratigraphy The study site is composed of quaternary alluvial and fluvial deposits that consist of poorly to well sorted gravels with sand and silt. 16 The gravel deposits in this area are known to be up to 60 m thick. 17 The source of these deposits is the Seaward Kaikoura range, which is composed of Pahu Terrane, a member of the Torlesse Supergroup. The Pahu Terrane is a well bedded sandstone to Mudstone with some poorly bedded sandstone. 18 Data and Methodology This study uses Lidar and GPS surveys to measure vertical and horizontal offset along the Horst- Graben, and uses Schmidt Hammer dating to constrain the age of the feature. Estimates of slip were calculated from the age and offset data. Vertical and Horizontal Displacement To calculate vertical displacement, the scarps were divided into four segments: A S-Facing scarp, Sections 1, 2, and 3 of the N-Facing scarp. For each segment, GIS was used to take Lidar-based elevation profiles above and below the scarp. The lower elevation profiles were subtracted from the upper elevation profiles to generate a series of data sets quantifying scarp height for each segment. Figures displaying the exported elevation data can be found in Appendix B. Section1 of the N-Facing scarp showed steady increase to a height of 2m, at which point it begins to flatten out, before dropping off as it is cross-cut by a river channel. The height values for the flat area at the peak of the scarp were averaged, yielding a measurement of 2.04 m of vertical offset. Uncertainties were calculated using the statistical First, the data used to find vertical offset was put in a histogram to ensure that it was close to a normal distribution. Then, using the mean and standard deviation of that data set, 1000 iterations of a random sampling test were run, where each random sample was used to generate a possible mean. This sampling created a normal distribution of probable alternative mean scarp heights. The maximum and minimum values for scarp height were taken from the 90% confidence interval of that data set, yielding a scarp height of 2.04±.06 m. The same method was used to create a height profile for Section2 of the N-Facing Scarp. Section2 is a relatively uniform height, so all of the heights along this scarp were included in the data set. This yielded a vertical offset of 0.4 ±0.2m. 16 (Coulter, 2007) 17 (Coulter, 2007) 18 (Coulter, 2007)

6 Section3 of the N-Facing scarp was considerably more complicated. The profile is clearly cut by a stream channel in one place, so that data was excluded from the scarp height calculations. Additionally, the scarp height profile includes a pair of distinct peaks of ~1.2m. In order to determine whether these peaks should be included in the data set, the upper and lower scarp profiles were graphed individually and compared. The peaks reflect a pair of bumps on the surface of the upper scarp rather than depressions on the lower scarp that would form as a result of post-rupture micro-scale sag ponding. The even surface on either side of these peaks indicates they were already present when faulting occurred, rather than the result of post-uplift erosion at the top of the scarp. The two peaks of ~1.2m have therefore been excluded from the data set used to calculate vertical offset for Section3 of the N-Facing scarp. A vertical offset of 0.8 ±0.2m was found for Section3 of the N-Facing scarp. This suggests that pre-uplift, there were two peaks of ~0.4 ±0.2m on an otherwise flat surface. A vertical offset value of 1.7 ±.3m was found for the S-Facing scarp. This segment has a relatively consistent surface, so all the offset data was included when calculating scarp height. Increased smallscale variation on the upper surface of this terrace (ranging from ~2m to ~0.8m of offset) resulted in a larger uncertainty value. The vertical displacement along the North and South Facing scarps is summarized by Figure 5. There are three distinct surface heights along the N-Facing scarp, implying a minimum of three uplift events. Because it is a separate feature, the S-Facing scarp s different height does not necessarily imply a fourth event. However, the vertical offsets are all close to or exact multiples of 0.4m. This suggests a series of uplift events of 0.4m each. Based maximum height of the current scarp profile (2m), we can infer five probable uplift events with an absolute minimum of three events. The probable displacement history of the Horst-Graben Feature is outlined below, and illustrated by Figure 6. 1) Faulting creates a 0.4m scarp, which is then eroded along Section2 and Section3 of the N-Facing Scarp. The river continues to flow, eroding most of the N-Facing scarp, although some bars remain. 1b) An inferred rupture event occurs along the same fault traces, raising Section1 of the N-Facing Scarp to 0.8m. The river erodes all traces of this event along Section2 and Section3 of the N-Facing Scarp. At this point in time, the Horst-Graben structure has begun to redirect the river so almost all of the uplift on the S-Facing Scarp is preserved, although some smaller stream channels cut down the scarp in places. 1c) An inferred rupture event occurs along the same fault traces, lifting Section1 up to create 1.2m of relief. The Horst-Graben feature has continued to redirect the river, and as the riverbed becomes shallower, some evidence of this faulting event is preserved as a bar on Section3 of the N-Facing Scarp. All of the uplift from this event is preserved on the S-Facing Scarp.

7 ) A third rupture event occurs, increasing the relief on Section1 from 1.2m to 1.6m. The Horst-Graben feature has continued to redirect the river since the previous events, and at this point the main riverbed has shifted elsewhere. However, one large channel remains, eroding Section2 of the N-Facing Scarp completely. All uplift on the S-Facing Scarp is preserved. 3) By the most recent faulting event, the Horst-Graben has completely redirected the river, and the 0.4 m of increase in relief is preserved along both the N- and S-Facing Scarps. Section1 rises up to 2m, Section2 is 0.4 ±0.2m in height, and Section3 is 0.8 ±0.2m in height in most places, with scarp height variations of up to ~1.2m caused by stream channels. The S-Facing scarp is just over 1.6m (1.7 ±0.3) high, with the height variation caused by old channels and bars ranging from ~0.8m to ~1.2m. Attempts were made to measure horizontal offset from an old stream bank that is cut by the N- Facing scarp, at the transition from Section1 to Section2. Unfortunately, a farm road and a drainage ditch have been constructed at the intersection. Comparison of the offset values derived from Lidar and GIS profiling, as well as field observations, suggest that the stream terrace has been modified to the point where it is not possible to accurately measure horizontal displacement. Age Calculation Previous work on Schmidt Hammer dating techniques provides the foundation for the age calculations in this study. By collecting Schmidt Hammer rebound values for a set of boulders that have been exposed at the surface since deposition, it is possible to estimate the average boulder hardness for a study site. The softer the boulders, the longer they have been exposed and weathered at the surface. 19 This relationship can be described by the equation: SH R = (a)(age) Where (SH R ) is the median rebound value for the site, and (a) is a constant unique to the area. In order to find the (a) value used this study, previous Schmidt Hammer data from the Waimangarara fan (location a, Figure 2) was compared to an established weathering rind age. 20 This resulted in an (a) value of Comparison to an (a) value for deposits from the Charwall river site (location b, Figure 2) suggests that our constant is reasonable. The procedure used to collect Schmidt Hammer data in this study is outlined in Stahl et al s 2013 paper. 30 clasts were sampled twice apiece in order to create two independent data sets. Because the sets were both normally distributed around similar means, they were combined. This yielded a median 19 (Stahl, et al., 2013) 20 (Pettinga & Wandres, 2005) 21 See Appendix C, Table 1 for detail on how (a) was calculated.

8 SH R value of 44. Using the previously calibrated (a) value, an age of 3700 ±800yrs can be assigned to the surface. Slip Rate and Extension Slip rate for the Horst-Graben feature can be calculated by identifying which surface the age date applies to, and then dividing vertical offset of that surface by the time since offset occurred. In order to identify the surface to which the age date applies, a series of GIS profiles were run across the sampling site. The profiles clearly show the paddock where samples were collected is the youngest of a series of old channels, constrained by a steep bank to the northwest and a gradually rising, slightly lower bank to the southeast. 22 This matches Section2 of the N-facing Scarp, which cuts across the most recently abandoned stream channel. Cross-cutting relationships between the stream channel and Section2 of the scarp indicate the most recent faulting event occurred sometime within the last 3700 ±800yrs. The movement of the river allows us to constrain the date of the faulting event even further. Figure 4 shows a series of abandoned terraces on the west side of the Hapuku River, indicating it is migrating east, away from the Horst- Graben. The evolutionary process of the scarp (Figure 6) shows that each uplift event causes more and more channels to be abandoned. Given that Section2 of the N-Facing scarp only records the most recent uplift event, that faulting event is likely what caused the youngest stream channel to be abandoned. As a result, the 0.4 ±0.2m of uplift recorded by Section2 probably occurred 3700 ±800yrs ago. This implies a vertical slip rate of 0.11 mm/yr, with a maximum slip rate of 0.21 mm/yr and a minimum slip rate of 0.05 mm/yr. Extension from this feature can be calculated from the vertical slip rate of the Horst-Graben. In this study, a probable scarp angle of 75 degrees and a minimum scarp angle of 60 degrees have been assumed. The results of these calculations are summarized by Table 1. Based on the vertical slip rate, this Horst graben has an extensional rate of 0.05 mm/yr, but could record up to 0.24mm/yr of extension. Discussion The newly discovered Horst-Graben feature projecting SE from the Hope Fault has been thoroughly examined using a combination of GIS analysis of Lidar, GPS data, and field observations. The scarp varies in height from 0.4 m to 2m. Different sections of the scarp preserve varying amounts of relief, but each section is approximately a multiple of 0.4m. This suggests that the scarp records a series 22 See Appendix C, Figure 13

9 of five uplift events, where each event has a vertical displacement of 0.4m. Increasing uplift appears to be forcing the Hapuku River eastward, and fewer and fewer stream channels erode portions of the scarp. The pattern of scarp uplift and river migration suggests that the last uplift event caused abandonment of the youngest faulted stream channel. This youngest stream channel is faulted only once, by Section2 of the N-Facing Scarp. Using Schmidt Hammer dating techniques, the abandoned stream channel surface was found to be 3700 ±800 years old. Based on age of the abandoned surface and the uplift of Section2 of the N-Facing Scarp, the scarp is vertically slipping at a rate of 0.05 to 0.21mm/yr. This indicates that the Horst-Graben feature represents 0.06 mm/yr of extension, although rates of up to 0.24 mm/yr are plausible. The Horst Graben sits to the North of the Hope Fault, in the area where the Hope Fault partitions off an estimated mm/yr of slip. 23 Although much of this slip is being absorbed by the Jordan Thrust, the presence of extension south of the Hope Fault validates the theory that some slip is being transferred into the Kaikoura Fault to 0.24mm of extension from the Horst-Graben is not very significant compared to the mm/yr that are partitioned off the Hope Fault. However, the extension rate calculated in this paper only refers to one feature. The slip that is transferred from the Hope Fault to the Kaikoura Fault would be the sum of the extension from all of the normal faulting south of the Seaward Section of the Hope Fault. A brief look at the Lidar data for the area around our study site reveals several potential normal faults, indicating that the 0.06 to 0.25 mm/yr calculated in this paper is only a small portion of the total extension in the area. Conclusion This study documents and analyzes a new Horst-Graben feature located between the Hope and Kaikoura Faults. While measurements of this feature provide concrete evidence that extension has occurred, additional research is required to estimate total slip transfer. Follow up work would include looking at a larger area using Lidar data, correcting previous mapping of the Hope Fault, determining whether the feature is currently active, as well as calculating extension along other normal faults in the area. Further investigation is important, as it will refine our understanding of the way slip is distributed within the Marlborough Fault System. Since estimates of maximum earthquake magnitude are calculated as a function of slip rate, current magnitude estimates might be incorrect. Depending on the quantity of slip transferred through extension, it may be necessary to revise our understanding of earthquake hazard in the Kaikoura Peninsula area. 23 (Van Dissen & Yeats, 1991)

10 256

11 Bibliography Barnes, P. M., & Audru, J.-C. (1999, April). Rcognition of active strike-slip faulting from high-resolution marine seismic reflection profiles: Eastern Marlborough fault system, New Zealand. GSA Bulletin, pp. v. 111; no 4; p Coulter, R. (2007). Tectonic Geomorphology and Seismic Hazard of the Mt.Fyffe Section of the Hope Fault. Master's Thesis, University of Canterbury, NZ. Cowan, H. (1989). An evaluation of the late Quaternary displacements and seismic hazard associated with the Hope and Kakapo faults, Amuri district, North Canterbury. Unpublished MSc thesis. Christchurch, New Zealand: University of Canterbury. Investigations and Monitoring Group, Environment Canterbury. (2007). Updated probabilistic Seismic Hazard Assessment for the Canterbury Region, Report no. U06/6. GNS Science Consultancy. Knuepfer, P. (1984). Tectonic geopmorphology and present-day tectonics of the Alpine Shear System, South Island, New Zealand. PhD thesis. Tuscon, Arizona, USA: University of Arizona. Knuepfer, P. (1988). Estimating ages of late Quaternary stream terraces from analysis of weathering rinds and solids. Bulletin of the Geological Society of America, 100, Knuepfer, P. (1992). Late Quaternary Slip Rate Variations, New Zealand. Tectonics, vol. 11, No. 3 Pg , June. Langridge, R. C., Hill, N., Pere, V., Pettinga, J., Estrada, E., & Berryman, K. (2003). Paleoseismology and slip rate of the Conway segment of the Hope Fault at Greenburn Sream, South Island, New Zealand. Annals of Geophysics, 46: Langridge, R., & Berryman, K. (2005). Morphology and slip rate ot the Huruni section of the Hope Fault, South Island, New Zealand. New Zealand Journal of Geology and Geophysics, 48: Langridge, R., Villamor, P., Basili, R., Almond, P., Martinez-Diaz, J., & Canora, C. (2010). Revised slip rates for the Alpine fault at Inchbonnie: Implications for plate boundary kinematics of South Island, New Zealand. Lithosphere, v. 2; no. 3; p Pettinga, J., & Wandres, A. (2005, 28 November- 1 December). Field Trip Guides. Kaikoura: Geological Society of New Zealand: 50th Anual conference. Stahl, T., Winkler, S., Quigley, M., Bebbington, M., Duffy, B., & Duke, D. (2013). Schmidt hammer exposure-age dating (SHD) of late Quaternary fluvial terraces in New Zealand. Earth Surface Process and Landforms, p. Wiley Online Library DOI: /esp Van Dissen, R. (1989). Late Quaternary faulting in the Kaikoura region, south-eastern Marlborough, New Zealand. MSc thesis. Corvallis, USA: Oregon State University. Van Dissen, R., & Yeats, R. (1991). Hope Fault, Jordan Thrust, and uplift of the Seaward Kaikoura Range, New Zealand. Geology,

12 Figures Figure Figure Figure 3

13 2) Current Theory 2) Alternate Theory Figure Figure Figure 6

14 Table 1 SUMMARY OF EXTENSION RATE CALCULATIONS Extension Extension max Extension min 75ᵒ scarp 0.06 mm/yr 0.11 mm/yr 0.02 mm/yr 60ᵒ scarp 0.13 mm/yr 0.24 mm/yr 0.05 mm/yr Figure Descriptions Figure 1: This map shows the Alpine Fault and the way that it splays out at the northern end of the island, with slip partitioning off onto several major faults that make up the Marlborough Fault system. It is edited from [Figure 1, Langridge et al, 2010]

15 Figure 2: Map showing the relevant and/or major faults near the study area, the study area itself, Schmidt Hammer data collection sites, and the Seaward Kaikoura range. Fault abbreviations are as follows: Clarence Fault -CF; Hope Fault (Conway segment) -HF (CS); Hope Fault (Mt. Fyffe Segment) -HF (MFS); Hope Fault (Seaward segment) -HF (SS); Jordan Thrust JT; Kaikoura Fault -KF; Kekerengu Fault KeF; Kohai Fault (KoF). Figure 3: Panel 1 shows the current theory on slip distribution, where the Jordan Thrust absorbs all 15-20mm/yr of slip, while Panel 2 shows the alternative theory proposed in this paper, where some slip is transferred to the Kaikoura Fault via extension. Figure 4: Facing N-NW, this image shows the study area, with the Horst-Graben structure that will be cataloged traced in red. Traces of the Hope Fault that have been previously mapped by Rose Coulter are shown in yellow-green. The X denotes the area where Schmidt hammer data was collected, and the Hapuku river flows into the foreground on the right side of the image. Figure 5: This image is a simplified representation of the profile of the N-Facing and S-Facing scarps at present day. The S-Facing scarp model is especially simplified- there are many smaller variations in surface, but only the most significant minimum and maximum height variations are shown in this diagram. Figure 6: This diagram shows the evolution of both the N-Facing and S-Facing scarps over time. Stages 1, 2, and 3 are the three known faulting events, while 1b and 1c are inferred based on a recurring vertical offset of 0.4m. The features shown on the S- Facing scarp are especially simplified- there are many smaller variations in surface, but only the most significant minimum and maximum height variations are shown in this diagram. Table 1: Sumarizes the extension rate calculations for the Horst Graben. These rates combine slip from both sides of the feature, and are calculated based on vertical slip rate Appendix A: Hope Fault Slip Rates Figure 7: The map above was modified from (Coulter, 2007). It provides a summary of slip variance along the Hope fault, dividing slip rates by section. For the Hurunui, Hope River, Conway, and Mt. Fyffe sections, some slip estimates fall outside of the ranges shown on Coulter s map (Van Dissen and Yeats, 1991) (Knupfer, 1992), but the overal variation in slip rate is well represented. Based on current available data, the seaward section has a much smaller slip rate than the 16±5 mm/yr given by Coulter s original map (Van Dissen and Yeats, 1991; Knupfer 1984; Van Dissen, 1989; Coulter, 2007). The value has therefore been removed in the above figure Segment (refers to Location details Publication Slip Rate (mm/yr)

16 Figure 7) Hurunui *assumes addition of Kakapo and Huruni Section slip Hurunui *assumes addition of Kakapo and Huruni Section slip Hurunui *assumes addition of Kakapo and Huruni Section slip Hurunui *assumes addition of Kakapo and Huruni Section slip Hurunui *assumes addition of Kakapo and Huruni Section slip Hurunui *assumes addition of Kakapo and Huruni Section slip Manuka Stream (MK) +Kakapo (KB) Glen Wye (GW) + Kakapo Glen Wye (GW) +Kakapo (KB) Manuka Stream (MK) +Kakapo (KB) Glen Wye (GW) +Kakapo (KB) Macs Knob, Mckenzie Fan+ Kakapo Knuepfer, 1984 [14-20] + [ ] Knuepfer, 1992 [ ]+[ ] Knuepfer, 1984; Van [14 to 24] +[ ] Dissen and Yates 1991 via Knuepfer 1988, Knuepfer, 1992 Cowan, 1989 [10.3±6] +[ ] Cowan, 1989 [11-17] +[4.7 t- 8.0] Langridge and Berryman, 2005; Langridge and Berryman, 2005 via Yang, 1991 Coulter 2007 via Cowan 1991; McGlone 1992 [ ]+[6.0±.04] Hope River Behavioural Whole segment estimate [10-14] Hope River Behavioural Hope River Knuepfer, 1992 [ ] Conway Whole segment [18-35] estimate Langeridge et al, 2003 and Coulter, 2007 via Freund, 1971; Van DIssen 1989, Bull, 1991, McMorran, 1991, Knuepfer, 1992; Pope, 1994 Conway Urquhart Stream Langeridge et al, 2003 [23±4] Conway Hossack Station Langeridge et al, 2003 via McMorran, 1991 Conway Charwell River (CW) Knupfer, 1984, 1988, 1992 Conway Sawyer s Creek (SC) Van Dissen, 1989; Langeridge et al, 2003; via Van DIssen 1989, Bull, 1991 [18±8] [17 to 48] [13-33] Conway Sawyer s Creek (SC) Van Dissen, 1989 Minimum of [28±8] Fyffe Goldmine Creek (GM) Van Dissen, 1989 [16±5] Seaward Hapuku River (HR) Knupfer, 1984 [1.7 to 2.5] Seaward Hapuku River (HR) Van Dissen, 1989 [ ] Seaward Not given Coulter, 2007 via Simpson, 1995 Seaward Hapuku River averaged Coulter, 2007 via Knupfer, 1989; Van Dissen, 1989 [3 to 5] [2 to 4.8] Table 2: Compilation of Hope fault slip rates. This table lists all of the Hope Fault slip rates considered in this paper, including specific locations at which they were taken (if given), as well as the paper in which they were found. Location details refer to the abbreviations in Figure 8, shown below, which was taken from (Van Dissen and Yates, 1991) 343

17 Figure 8: Shows locations where some Hope Fault slip measurements were taken

18 Appendix B: Original Scarp Profiles 2.5 Height of Section 1 of N-Facing Scarp Height (m) Distance Along Scarp (m) Figure 9: Shows scarp height along section 1 of the N-Facing scarp of the Horst-Graben structure. It illustrates how section 1 of the scarp steadily declines as it moves from east to west, starting at a maximum height of 2m. 0.8 Height of Section 2 of N-Facing Scarp Height (m) Distance along scarp (m) Figure 10: shows scarp height along section 2 of the N-Facing scarp of the Horst-Graben Structure

19 Scarp Height (m) Figure 11: This graph shows the height for section 3 of the north facing limb of the Horst-Graben. The main surface is, on average, 0.8m in height. The two peaks of ~1.2m at about 125 and 150 m along the profile that has been separated out, as it is likely a remnant from an older scarp. More detail on these two peaks is provided by Figure 11. The hole from about 30m to 70m appears to be an old streambed, and so has been omitted when assessing the height of the scarp. Elevation (m) Height of Section 3 of N-Facing Scarp Distance Along Scarp (m) Upper and Lower Terrace Surfaces: N-Facing Scarp Profile 3 Main Scarp surface Potential remnants of older scarp Distance Along Scarp (m) Upper TCE Lower TCE Figure 12: This graph compares the upper and lower surfaces of section 3 of the north facing scarp. It shows that the two peaks in scarp height, visible in Figure 10, are due to variation on the top surface, not the bottom. It suggests that the height spikes are likely remnants of a higher surface, rather than reflecting some kind of hole or swampy depression at the base of the scarp. 363

20 Appendix C: Age Calculation CALIBRATION OF AN A VALUE USING SH R (a)(age).189 Median SH R value from Waimangarara 48.5 Weathering rind age for Waimangarara 2200 ±300 Calibrated a value Uncertainty in (a) *based on Weathering rind uncertainty ±5.6 Table 3: Shows the steps used to calibrate an (a) value for Stahl et al 2013 s Schmidt Hammer dating equation. The uncertainty for (a) was derived using the uncertainty in age from the weathering rind dating. 118 Profiles of Schmidt Hammer Sampling Site Elevation (m) Transect1 112 Transect2 111 Transect Distance along Transect (m) Figure 13: Profiles of the area where the Schmidt Hammer samples were taken. The series of profiles clearly show the drainage ditches dug by the farmer as sharp elevation drops, reflecting the change in profile from Section1 to Section2 of the N-Facing scarp. Between the two drainage ditches is a flat lower surface, and after the second drainage ditch, the ground begins to slope upward to a higher surface, reflecting the change in profile from Section2 to Section3 of the N-Facing scarp. Schmidt Hammer data was taken in between the two drainage ditches