The Cephalonia-Lekfada Transform Fault Zone (CLTFZ) lies at the transition between the continental subduction of Adria microplate underneath Eurasia to the north, and the oceanic subduction of the Nubian plate along the Hellenic Arc to the south.Since its onset, estimated around the Late Miocene-early Pliocene, the CLTFZ is considered to have accumulated between 40 and ~80 km right-lateral displacement, with most of the offset occurring in the last ~5 Ma. Currently, the intense crustal deformation characterising the area results in high seismicity affecting the western part of Lefkada and Cephalonia islands, as demonstrated by several Mw>6 earthquakes that struck this narrow region in the last two decades (Mw 6.2 Lefkada, 2003; Mw 6.1 and Mw 5.9 Cephalonia, 2014; Mw 6.4 Lefkada, 2015).We use conventional structural mapping and geomorphic analysis to identify and measure the main onshore faults and their kinematic evolution along the western coast of Cephalonia and Lefkada islands.We observe that the topography of the islands is mostly tectonically controlled: right-lateral transpression is expressed as elongated ridges, trending ~N15 and delimited by thrusts. Transtensive, NE-SW-trending en échelon faults develop on the ridge crests, where measured fault throw indicates up to 1.5 km NW-SE-directed extension on a single ridge. Similar structures have been recently observed in analogue modelling experiments, forming as Riedel-shears in the later stages of the transpressional system evolution.Inactive, and hence older faults seem to have formed as opening fractures in an extensional regime (~W-E). The fractures are filled with calcite veins displaying multiple growth generations, which suggests formation in a fluid-rich environment. Active faults display at least two generations of striae indicating pure dip-slip and strike-slip/oblique movement. Where visible, the cross-cutting relationship between the two generations indicates a first phase of normal faulting followed by more recent transcurrent faulting. This is in agreement with geodetic data, reporting a dominant horizontal component of movement during the recent earthquakes.The overall fault analysis indicates an important strain partitioning along the CLTFZ, providing relevant constraints to the seismotectonic pattern of the region.

The eastern Adriatic margin is composed by an Ocean-Continent Transition lithosphere (OCT), resulting in the southwards along-strike variation from collision to subduction. The Cephalonia-Lefkada Transform Fault zone (CTF) is a right-lateral strike-slip fault system located above the OCT and associated to this kinematic transition. The CTF is generally considered a proto-STEP fault, that is the surface expression of the early-stage propagation of a vertical slab tear (STEP) from the subducting lithosphere to the overriding plate. However, the existence of a slab tear is debated. The poorly constrained structural evolution of the CTF prevents to understand how the upper plate accommodates deformation above the OCT. We fill this gap by exploring onset, kinematic evolution, and geodynamics of the CTF system using onshore field observations and structural analysis. We find that the CTF developed as a right-lateral transpressional system characterized by strain partitioning into thrusting and strike-slip faulting since at least the late Pliocene. As the margin along the CTF progressively rotated clockwise due to differential convergence rates, the margin-normal component of deformation, accommodated by thrusts, decreased, while shear strain, accommodated by strike-slip faulting, increased. This ongoing strain partitioning is supported by published focal mechanisms and offshore seismic-reflection data. Our observations are consistent with a proto-STEP fault interpretation for the CTF. Joint evidence from the geometry of the fault system onshore and offshore, coupled with distinct partitioning of the strain along the CTF, suggest the absence of a slab tear below the CTF, favoring the hypothesis of a bent but still-intact slab.

Sets of marine terraces, sediments, and paleoshorelines are commonly found in forearc regions worldwide. A common assumption holds that crustal uplift prevents these features from littoral erosion. Here, we study the vertical deformation of Karpathos, a forearc island in the eastern Mediterranean, whose long axis extends at a high angle to the strike of the Hellenic Subduction System (HSS). We target three key coastal localities along the island to discuss spatial and temporal variability of vertical motion. We mapped sets of up to 19 marine terraces per locality, with elevations ranging from 1.5 to similar to 350 masl. Ages for terraces and sediments are constrained by radiocarbon (<31 masl) and Sr-isotope (2-310 masl) dating, and range from 2.4 ka to similar to 4.3 Ma. Data analysis shows that average uplift rates are up to two orders of magnitude faster over shorter (less than or similar to 100 ka) than longer (greater than or similar to 100 ka) timescales, in agreement with other local and global data sets. Further, we find evidence for multiple marine reoccupations of late Pleistocene terraces, indicating that carbonate beachrock is often resistant to multiple interactions with sea-level. Neogene marine sequences that witness longer periods (similar to 4 Ma) show signs of alternating vertical motion. Using this novel data set, we explore the effects of various mechanisms (i.e., upper-plate normal faulting, splay-thrust faulting, basal underplating) on the spatial and temporal patterns of vertical deformation. Although the contribution of each mechanism to the net vertical deformation cannot be isolated with certainty, our results show that none alone could account for the observations. Plain Language Summary In this study, we focus on understanding how the landmass of Karpathos Island, in the Hellenic Subduction System in the Mediterranean Sea, moved vertically over time. We focus mainly on marine terraces, which are wave-cut platforms near the sea forming staircase-like topography. The age of these platforms has been constrained by dating fossil shells, shell fragments, and soils that mantle the terraces: for young (closer to the sea-level) markers we used the isotope Carbon-14, while for older terraces (further inland) Strontium-87. We found that the island of Karpathos subsided prior to similar to 4.3 Ma, but since then it experiences uplift. From our analysis, we find that the vertical motion of the island is the result of, at least, three interrelated processes: (a) sediment underplating, that scrapes sediments from the down-going plate during subduction and attaches them to the base of the upper plate, pushing it upwards; (b) large earthquakes that occur either at the interface of two converging plates or on large faults that splay from this interface; and (c) smaller earthquakes produced by the horizontal stretching of the Aegean crust.

&lt;p&gt;The eastern Mediterranean island of Crete is located on the overriding plate of the Hellenic subduction thrust which is curved and changes strike from ~170&amp;#176; to ~50&amp;#176; in a west to east direction. Crete is located in the zone of maximum curvature of the subduction thrust. Basin and range topography together with prominent limestone scarps indicate that Quaternary deformation at the ground surface on Crete is dominated by normal faults with slip rates of up to ~1 mm/yr. These active faults comprise two primary sets that strike N-NNE (0-30&amp;#176;) and E-ESE (90-120&amp;#176;), with the more easterly faults dominating in southern Crete. Each fault set is characterised by dip slip and together they accommodate coeval W-WNW and N-NNE crustal extension. The E-ESE normal faults are approximately parallel to the strike of the subducting North African plate and form part of a regional fault system that swings in strike in sympathy with depth contours on the top of the concave northwards plate. By contrast, N-NNE normal faults are sub-parallel to the line of maximum curvature on the subduction thrust. These geometric relationships support the view that normal faulting on Crete formed, at least partly, in response to Cenozoic slab retreat (e.g., Jolivet et al., 2013), which continued into the Quaternary. In this model contemporaneous multi-directional crustal extension on Crete is driven by geologically simultaneous westward and southward retreat of the slab.&lt;/p&gt; &lt;p&gt;&amp;#160;Jolivet, L., Faccenna, C., Huet, B., Labrousse, L., Le Pourhiet, L., Lacombe, O., et al. (2013). Aegean tectonics: Strain localisation, slab tearing and trenchretreat. Tectonophysics, 597&amp;#8211;598, 1&amp;#8211;33. https://doi.org/10.1016/j.tecto.2012.06.011&lt;/p&gt;

The fluctuations of the Rare Earth Elements and Yttrium (REE-Y) concentrations on exhumed carbonate normal fault scarps may reveal the number and size of paleoearthquakes that exposed the scarp subaerially. This is because, prior to each large-magnitude earthquake, narrow (<50 cm) sections of the fault plane which are in direct contact with the soil become enriched in REE-Y before they are exhumed co-seismically, together with deeper, non-enriched, scarp sections. Following exhumation, depletion in REE-Y commences on both the enriched (i.e. 'soil rupture zone') and non-enriched (i.e. 'rock rupture zone') scarp sections. Although these processes are commonly described to occur on carbonate scarps, the mechanisms through which they operate remains poorly understood. Here, we present a series of laboratory tests that mimic the natural process of REE-Y enrichment/depletion to elucidate the mechanism of REE-Y impregnation. Our results indicate a fast uptake of REE-Y by the carbonate plane, when in contact with soil, either as (REE, Y)2(CO3)3 precipitate or by adsorption on calcite surfaces. The source of REE-Y in soil solution is released in a "pulses" due to alternations of dry and wet periods, characteristic of Mediterranean climatic conditions. Organic matter oxidation during the first rain events, triggers the Mn reductive dissolution and the release of REE-Y into the soil solution. The pH decrease due to organic matter dissolution is buffered by calcite, especially in the vicinity of the scarp, where calcite dissolution and re-precipitation occurs with a marked pH oscillation between 9.3 and 7.7. Further, comparison of these results with empirical data from three co-seismically exhumed fault scarps in Greece and Italy places quantitative constraints on the timing of these processes: the REE-Y enrichment within the 'soil rupture zone' may reach a maximum of -50% in about 500 years (+0.53 & mu;g/kg/year), while the REE-Y depletion from the scarp is slow (-0.021 & mu;g/kg/year), with a maximum recorded retention time of -16 ka. These enrichment and depletion characteristics work together to preserve paleoearthquake signal on carbonate scarps. Thus, this methodology is a valuable tool for quantifying the number of past earthquakes on carbonate fault scarps and allows more targeted use of expensive dating techniques (i.e. with cosmogenic nuclides) in order to derive the precise timing of these paleoearthquakes.

The Kaikoura Earthquake uplifted Kaikoura Peninsula by <=similar to 1 m. Uplift in 2016 mainly resulted from slip on an offshore thrust fault (OSTF), modelled to splay from the plate-interface, and was further influenced by slip on two newly identified faults (Armers Beach Fault, ABF; Te Taumanu Fault, TTF) mapped onshore from differential lidar (D-lidar). Forward dislocation modelling indicates that 2016 peninsula uplift can be reproduced by mean slip of similar to 2.3 m on the OSTF and 0.25-0.5 m on the ABF and TTF. The variable co-seismic uplift recorded during the 2016 earthquake differs from the near-uniform (1.2 +/- 0.2 degrees) northwest tilting of MIS5c (96 +/- 5 ka) and MIS5e (123 +/- 5 ka) marine terraces; these ages are constrained by Optically Stimulated Luminescence (OSL) dating and correlation to sea-level curves. Tilting of Late Quaternary marine terraces can be primarily reproduced by slip rates of similar to 0.8-2.7 mm/yr on the OSTF and 0.3-0.6 mm/yr on the ABF. Slip on the TTF is not required to produce tilting of the marine terraces, suggesting that it may have ruptured less frequently than the OSTF and ABF in the Late Quaternary. The OSTF links 2016 ruptures north and south of Kaikoura, with the earthquake rupturing an interconnected network of faults.

Located on the overriding plate of the Hellenic subduction margin, the 250 km-long island of Crete offers a unique opportunity to study curved-forearc deformation. The African-Eurasian plate-convergence of ~40 mm/yr (~80 %) is primarily accommodated aseismically, but intense seismicity is recorded at the plate-interface and a reverse splay faults along the Hellenic trough; frequent M6+ earthquakes and (at least one) tsunami-genic event, causing up to 10 m of paleoshoreline uplift in western Crete, are reported. Global Navigation Satellite System (GNSS) data revealed N-S shortening of ~2 mm/yr within western Crete due to pure plate convergence. Further east, the curved subduction trench accommodates increased oblique slip, causing E-W extension of ~2 mm/yr in eastern Crete.Recently, the European Ground Motion Service published dense InSAR surface deformation data in East and Up direction of whole Europe. The InSAR time-series comprise positioning samples every six days, respectively, every ~50 m, and, in Crete, exhibit long-wavelength deformation signals caused by deep-rooted, tectonic sources that are overlaid by (often seasonally-modulated) signals originating in shallow aquifers. We analyze these time-series in space and time and validate the results using available GNSS rates, a seismic catalog and an active fault data base. Preliminary results suggest a slight eastward tilt of Crete, which is not confirmed by published GNSS rates, and has to be investigated further. Spatially-confined uplift of up to ~5 mm/yr are observed at the karstic Omalos plateau, and up to ~30 mm/yr subsidence in the Messara basin, both probably related to groundwater replenishment/abstraction. Relative eastward motion increases towards eastern Crete, particularly in the fault zones embracing Mirabello bay and east of it, thus confirming the aforementioned E-W extension, and towards the southern coast.

As well as slip on a primary fault plane, earthquakes can produce slip on neighbouring faults which are not directly linked to the main source. This slip is called syn-seismic. With modern space-borne observation techniques, we observe syn-seismic slip down to a few centimeters on active faults nearby the source. An excellent example is the mapped slip on secondary faults during the 2019 Ridgecrest earthquake sequence in California. The overall spatial pattern of syn-seismic slip with respect to the main fault suggest that these faults respond to local stress changes caused by the main shock.Data that enable the detection of surface fault slip on such small scale are provided by optical and radar satellites which allow a very high precision with high spatial resolution. In particular, short revisit times of these satellite observations lead to high coherence between images matched in pixel-offset and radar interferometric techniques.We present further examples of syn-seismic fault slip during ~M6 earthquakes from different regions, such as those recorded in Greece in 2021 (Tyrnavos and Arkalochori) and 2020 in Tibet (W Xizang and near Xegar). We use Sentinel-1 interferometric wide-swath SAR acquisitions, which we process on the highest spatial resolution and apply weak filtering only. Our examples have in common that their syn-seismic fault activation reveals slip of a few centimeters only, persistently along a section of the fault’s length. The slip directions commonly appear to follow the coseismic surface displacement gradients which, in some cases, results in reverse slip on long-term normal faults. The activated faults were either faults previously mapped or concealed faults which were identified due to InSAR.It is difficult to estimate the depth of syn-seismic fault slip and therefore how much strain has been released due to localized stress changes. We are also uncertain of the extent to which this small slip release contributes to the long-term displacement and displacement rate on faults and whether its contribution should be included in dislocation fault slip models. Our compilation suggests that syn-seismic slip is rather common, despite the rarity of previous observations, and is now detectable only because of improved resolution provided by InSAR data.

Karpathos is a roughly north-south oriented island that emerges between Crete and Rhodes in the forearc of the eastern Hellenic subduction system. It extends for ~60 km to the north of the 40 km contour of the plate interface depth. Further, the northern part of the island is confined to a N-S trending Horst bounded by two large normal faults that shape the seafloor off both, the eastern and western shore. Furthermore, many normal faults, mainly in the north, strike parallel to the Horst and shape the topography onshore. Given the location and the structural configuration of the island, we expect that multiple processes are reflected in both the sedimentary and morphological record of vertical movement. Marine terraces and paleo-cliffs are observed all around the island recording its vertical movements over the last ~1 Ma. Moreover, sedimentary basins in the southern and central parts of the island are excellent archives of long-term uplift interrupted by subsidence over the last ~4.5 Ma. Twenty-five samples were collected at elevations between 1 and ~310 masl. We have gathered six (n=6) age/elevation data-points obtained by Sr-isotope dating, and nineteen (n=19) age/elevation data-points by radiocarbon dating. We explored the likelihood of different hypotheses on what drives the uplift: whether it is driven by upper-crust normal faults, megathrust earthquakes, underplating, or a combination of these phenomena. We present preliminary results on both the temporal and spatial fluctuations of the vertical movement of Karpathos.

Upper-plate normal faults along forearcs often accumulate slip during >Mw 6 earthquakes. Such normal faults traverse the forearc of the Hellenic Subduction System (HSS) in Greece and are the focus of this study. Here, we use detailed field-mapping and analysis of high-resolution Digital Elevation Models (DEMs) to study 42 active normal faults on the islands of Kythira and Antikythira in the Aegean Sea. Onshore fault kinematic data are complemented by seabed bathymetry mapping of ten offshore faults that extend along the Kythira-Antikythira Strait (KAS). We find that normal faults in the KAS have lengths of ∼1–58 km and scarps ranging in height from 1.5 m to 2.8 km, accommodating, during the Quaternary, trench-orthogonal (NE-SW) extension of ∼2.46 ± 1.53 mm/a. Twenty-eight of these faults have ruptured since the Last Glacial Maximum, with their postglacial (16 ± 2 ka) displacement rates (0.19–1.25 mm/a) exceeding their Quaternary (≤0.7–3 Ma) rates (0.03–0.37 mm/a) by more than one order of magnitude. Rate variability, which is more pronounced on short (<8 km) faults, is thought to arise due to temporally clustered paleoearthquakes on individual KAS faults. When displacement accumulation is considered across the entire onshore fault network, rate variability between the two time-intervals examined decreases significantly (2.79 ± 0.41 vs 1.29 ± 0.99 mm/a), a feature that suggests that earthquake clustering in the KAS may occur over ≤16 ka timescales.

Large magnitude (Mw ∼ ≥6) earthquakes in extensional settings are often associated with simultaneous rupture of multiple normal faults as a result of static and/or dynamic stress transfer. Here, we report details of the coseismic breaching of a previously unrecognized large-scale fault relay zone in central Greece, through three successive normal fault earthquakes of moderate magnitude (Mw 5.7–6.3) that occurred over a period of ∼10 days in March 2021. Specifically, joint analysis of InSAR, GNSS and seismological data, coupled with detailed field and digital fault mapping, reveals that the Tyrnavos Earthquake Sequence (TES) was accommodated at the northern end of a ∼100 km wide transfer structure, by faults largely unbroken during the Holocene. By contrast, the southern section of this relay zone appears to have accrued significant slip during Holocene. InSAR-derived displacements agree with the loci of eight subtle, previously undetected, faults that accommodated coseismic and/or syn-seismic normal fault slip during the TES. Kinematic modeling coupled with fault mapping suggests that all involved faults are interconnected at depth, with their conjugate fault-intersections acting largely as barriers to coseismic rupture propagation. We also find that the TES mainshocks were characterized by unusually high (>6 MPa) stress-drop values that scale inversely with rupture length and earthquake magnitude. These findings, collectively suggest that the TES propagated north-westward to rupture increasingly stronger asperities at fault intersections, transferring slip between the tips of a well-established, but previously unrecognized, relay structure. Fault relay zones may be prone to high stress-drop earthquakes and associated elevated seismic hazard.

The c. 15 km-long Ngapouri-Rotomahana Fault (NRF) is a major splay of the Paeroa Fault at the eastern margin of the modern Taupo over bar Rift, the active tectonic structure embedded within the Taupo over bar Volcanic Zone of North Island, New Zealand. The NRF and Paeroa Fault extend to the southern margin of the Okataina Volcanic Centre (OVC) and lie southwest of the Tarawera vent lineation, which is the source of approximately half of the eruptions of the OVC in the past 25 cal. ka BP. Here, we explore volcano-tectonic relationships between the OVC and the NRF and Paeroa Fault. Collective evidence used in our analysis includes: volcanic processes interpreted as occurring during the historic 1886 Tarawera (basalt) and the prehistoric 1314 +/- 12 CE Kaharoa (basalt triggered rhyolite) eruptions, both on the Tarawera vent lineation; exposures in five trenches excavated across the NRF and seven trenches across the Paeroa Fault; data on a series of explosion craters formed to the southwest of the volcano associated with the -1314 CE Kaharoa eruption and the Rotoma rhyolite (-9.4 cal. ka BP) eruption from the OVC; and mafic dykes that primed several of the OVC eruptions. Data from the twelve trenches on the two faults reveal eight surface fault ruptures since 15.6 cal. ka BP, with most closely coinciding with volcanic eruptions, providing a first-order indication of probable causality. Three principal modes of interaction are identified. Firstly, large displacement events on the Paeroa fault, arguably immediately prior to the Mamaku and Rotoma rhyolite eruptions (-7.9 and -9.4. cal. ka BP, respectively) and on the NRF immediately prior to the -1314 CE Kaharoa eruption are candidates for earthquake static or dynamic stress triggers for those explosive eruptive events. Secondly, basalt dyke intrusion was also involved in the initiation of the Kaharoa eruption, so the spatial and temporal relationships between dyke intrusion, smaller displacement fault ruptures and initiation of the Kaharoa eruption appear closely connected. Thirdly, faulting events that are interpreted as co- or posteruption may be the result of stress triggers associated with magma chamber deflation.

&lt;p&gt;Karpathos is a roughly north-south oriented island that emerges between Crete and Rhodes in the forearc of the eastern Hellenic subduction system. It extends for ~60 km to the north of the 40 km contour of the plate interface depth. Further, the northern part of the island is confined to a N-S trending Horst bounded by two large normal faults that shape the seafloor off both, the eastern and western shore.&amp;#160; Furthermore, many normal faults, mainly in the north, strike parallel to the Horst and shape the topography onshore. Given the location and the structural configuration of the island, we expect that multiple processes are reflected in both the sedimentary and morphological record of vertical movement. Marine terraces and paleo-cliffs are observed all around the island recording its vertical movements over the last ~1 Ma. Moreover, sedimentary basins in the southern and central parts of the island are excellent archives of long-term uplift interrupted by subsidence over the last ~4.5 Ma. Twenty-five samples were collected at elevations between 1 and ~310 masl. We have gathered six (n=6) age/elevation data-points obtained by Sr-isotope dating, and nineteen (n=19) age/elevation data-points by radiocarbon dating. We explored the likelihood of different hypotheses on what drives the uplift:&amp;#160; whether it is driven by upper-crust normal faults, megathrust earthquakes, underplating, or a combination of these phenomena. We present preliminary results on both the temporal and spatial fluctuations of the vertical movement of Karpathos.&lt;/p&gt;

Geohazards and risks involve time-varying phenomena; thus, such evaluations require multidimensional analysis using a variety of numerical process models. This chapter presents several case studies that have been selected to illustrate the benefits of using 3-D geological models as part of hazard and risk investigations. The first case study describes the development of 3-D geological models for Christchurch, New Zealand to guide urban reconstruction plans following major earthquakes in 2010 and 2011. The second case study explores the added value provided by 3-D modeling and visualization of typical siteinvestigation data. The third case study is an example of linking 3-D geological models to multiple process-based models to provide better predictions of the rate of cliff erosion along section of the east coast of England. The fourth case study describes how 3-D modeling improved the evaluation of the extent and geochemical characteristics of contaminated soils in an area of Nantes, France, that is undergoing urban redevelopment.

Active normal faults on the eastern Mediterranean island of Crete form prominent limestone scarps together with basin and range topography. These faults mainly strike E-ESE and N-NNE in southern and northern Crete, respectively, with fault sets commonly intersecting and northern-trending faults a factor of three more abundant. Displacements, lengths and displacement rates have been analysed for 84 active faults sampled over 2±0.5 Ma (long term) and 16.5±2 ka (short term) time-intervals, with about half showing no resolvable short-term activity. Active faults record earthquake processes on timescales of thousands to millions of years and constrain sampling biases, which can lead to under and over estimates of the numbers, rupture lengths, recurrence intervals and single event displacements of paleoearthquakes. The available data indicate no fault propagation and, for the Quaternary, higher displacement rates on longer faults, supporting a model in which fault lengths and maximum earthquake magnitudes were established early in the development of the fault system. Short-term displacement rates (0.09-1.2 mm/yr) are generally higher than long-term rates (0.002-0.7 mm/yr), with a factor of four disparity in the average recurrence intervals for the two time periods (~2.5 kyr vs ~11 kyr). We attribute these differences to ‘clustering’ of &gt;Mw 6 earthquakes on individual faults over millennial timescales, and to preferential sampling of the most seismically active faults in the post-~16.5 kyr time interval (i.e. faults with highest displacement rates or mid ‘cluster’). Displacement rates are comparable when averaged for each time interval on the longest faults (&gt;10 km), interpreted to indicate that for these faults earthquake ‘clustering’ spans time-intervals of 16.5±2 kyr or less. Paleoarthquakes &gt;Mw 6 on Crete are a factor of three more frequent than historical events for the last 100 yrs, which could be partly due to paleoevents rupturing multiple faults, either in the same event or in triggered slip events.

Abstract Active normal faults on the Mediterranean island of Crete form prominent limestone scarps together with basin and range topography. These faults mainly strike E‐ESE and N‐NNE in southern and northern Crete, respectively, with fault sets commonly intersecting and northerly trending faults being a factor of 3 more abundant. Lengths, displacements, and displacement rates have been analyzed for 84 active faults sampled over 2 ± 0.5 Ma (long‐term) and 16.5 ± 2 ka (short‐term) time‐intervals, with half showing no resolvable short‐term activity. Active faults record earthquake processes on timescales of thousands to million years and constrain sampling biases, which can lead to under and over estimates of fault parameters. The available data provide no evidence for fault propagation and support a model in which fault lengths were established early in the development of the fault system. Short‐term displacement rates (0.09–1.2 mm/year) are generally higher than long‐term rates (0.002–0.7 mm/year), with a factor of 4 disparity in the average recurrence intervals for the two time periods (∼2.5 Kyr vs. ∼11 Kyr). We attribute these differences to “clustering” of surface‐rupturing (e.g., >Mw6) earthquakes on individual faults over millennial timescales, and to preferential sampling of the most seismically active faults during the short‐term. Displacement rates are comparable when averaged for each time interval on the longest faults (>10 km), indicating that for these faults earthquake “clustering” spans time‐intervals of <∼16.5 Kyr. Paleoerthquakes > Mw6 on Crete are at least three times more frequent than historical earthquakes since ∼1920, possibly because multi‐fault surface‐rupturing earthquakes are double counted in the paleo‐record.

The 2016 Mw=7.8 Kaikōura earthquake (South Island, New Zealand) caused widespread complex ground deformation, including significant coastal uplift of rocky shorelines. This coastal deformation is used here to develop a new methodology, in which the upper living limits of intertidal marine biota have been calibrated against tide-gauge records to quantitatively constrain pre-deformation biota living position relative to sea level. This living position is then applied to measure coseismic uplift at three other locations along the Kaikōura coast. We then assess how coseismic uplift derived using this calibrated biological method compares to that measured using other methods, such as light detection and ranging (lidar) and strong-motion data, as well as non-calibrated biological methods at the same localities. The results show that where biological data are collected by a real-time kinematic (RTK) global navigation satellite system (GNSS) in sheltered locations, this new tide-gauge calibration method estimates tectonic uplift with an accuracy of ±≤0.07 m in the vicinity of the tide gauge and an overall mean accuracy of ±0.10 m or 10 % compared to differential lidar methods for all locations. Sites exposed to high wave wash, or data collected by tape measure, are more likely to show higher uplift results. Tectonic uplift estimates derived using predictive tidal charts produce overall higher uplift estimates in comparison to tide-gauge-calibrated and instrumental methods, with mean uplift results 0.21 m or 20 % higher than lidar results. This low-tech methodology can, however, produce uplift results that are broadly consistent with instrumental methodologies and may be applied with confidence in remote locations where lidar or local tide-gauge measurements are not available.

Abstract. The 2016 Mw 7.8 Kaikōura Earthquake (South Island, New Zealand) caused widespread complex ground deformation including significant coastal uplift of rocky shorelines. This coastal deformation is used here to develop a new methodology, in which intertidal marine biota have been calibrated against tide-gauge records to quantitatively constrain pre-deformation biota living depths relative to sea level. This living depth is then applied to biologically measured tectonic uplift at three other locations along the Kaikōura coast. We also test how tectonic uplift measured using this calibrated marine biota compares to vertical deformation measured, at the same localities, using instrumental methods [Light Detection and Ranging (LiDAR) and strong motion data], and non-calibrated biological methods. Data show that where biological data is collected by RTK-GNSS in sheltered locations, this new tide-gauge calibration method estimates tectonic uplift with an accuracy of ± ≤ 0.07 m in the vicinity of the tide-gauge, and an overall mean accuracy of ± 0.10 m or 10 % compared to differential LiDAR methods for all locations. Sites exposed to high wave wash, or data collected by tape-measure, are more likely to show higher uplift results. Tectonic uplift estimates derived using predictive tidal charts produce overall higher uplift estimates in comparison to tide-gauge calibrated and instrumental methods, with mean uplift results 0.21 m or 20 % higher than LiDAR results. This low-tech methodology can, however, produce uplift results that are broadly consistent with instrumental methodologies and might be applied with confidence in remote locations where satellite data or local tide-gauge measurements are not available.

Subduction systems globally terminate, allowing plate-motion to be transferred from the oceanic megathrust onto continental and/or oceanic transform faults. The mechanism of this kinematic transition over earthquake timescales is, however, poorly understood due to a lack of relevant data. Here, we study the 2016 Mw 7.8 Kaikōura Earthquake in New Zealand, the first large instrumentally-recorded earthquake across a subduction-termination, to investigate this transfer mechanism in detail. We find that the Kaikōura Earthquake, unlike standard subduction earthquakes globally, involved a predominance (∼80%) of coseismic-slip on upper-plate faults and minor triggered-slip on the underlying oceanic subduction-thrust. In the months following the earthquake, the subduction-thrust accommodated most of the earthquake's afterslip down-dip of its co-seismic rupture zone. This top-down strain-release mechanism is in accord with local geological, geodetic and historical seismicity data which suggest that the bulk of plate-convergence (>75%) is accommodated in the upper-plate. We suggest, therefore, that this alternative strain-release mechanism, which is distinct from standard plate-boundary earthquakes, is characteristic of subduction-terminations and results in the majority of seismic/tsunami hazard being on steep near-surface faults.