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1. Holocene Rupture History of the Central Teton Fault at Leigh Lake, Grand Teton National Park, Wyoming

   https://doi.org/10.1785/0120190129  

   Zellman, Mark S.; DuRoss, Christopher B.; Thackray, Glenn D.; Personius, Stephen F.; Reitman, Nadine G.; Mahan, Shannon A.; Brossy, Cooper C. (November 2019, Bulletin of the Seismological Society of America)

   Abstract Prominent scarps on Pinedale glacial surfaces along the eastern base of the Teton Range confirm latest Pleistocene to Holocene surface‐faulting earthquakes on the Teton fault, but the timing of these events is only broadly constrained by a single previous paleoseismic study. We excavated two trenches at the Leigh Lake site near the center of the Teton fault to address open questions about earthquake timing and rupture length. Structural and stratigraphic evidence indicates two surface‐faulting earthquakes at the site that postdate deglacial sediments dated by radiocarbon and optically stimulated luminescence to ∼10–11  ka. Earthquake LL2 occurred at ∼10.0  ka (9.7–10.4 ka; 95% confidence range) and LL1 at ∼5.9  ka (4.8–7.1 ka; 95%). LL2 predates an earthquake at ∼8  ka identified in the previous paleoseismic investigation at Granite Canyon. LL1 corresponds to the most recent Granite Canyon earthquake at ∼4.7–7.9  ka (95% confidence range). Our results are consistent with the previously documented long‐elapsed time since the most recent Teton fault rupture and expand the fault’s earthquake history into the early Holocene. 

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2. Holocene Paleoseismology of the Steamboat Mountain Site: Evidence for Full-Length Rupture of the Teton Fault, Wyoming

   https://doi.org/10.1785/0120200212  

   DuRoss, Christopher B.; Zellman, Mark S.; Thackray, Glenn D.; Briggs, Richard W.; Gold, Ryan D.; Mahan, Shannon A. (December 2020, Bulletin of the Seismological Society of America)

   null (Ed.)

   ABSTRACT The 72-km-long Teton fault in northwestern Wyoming is an ideal candidate for reconstructing the lateral extent of surface-rupturing earthquakes and testing models of normal-fault segmentation. To explore the history of earthquakes on the northern Teton fault, we hand-excavated two trenches at the Steamboat Mountain site, where the east-dipping Teton fault has vertically displaced west-sloping alluvial-fan surfaces. The trenches exposed glaciofluvial, alluvial-fan, and scarp-derived colluvial sediments and stratigraphic and structural evidence of two surface-rupturing earthquakes (SM1 and SM2). A Bayesian geochronologic model for the site includes three optically stimulated luminescence ages (∼12–17  ka) for the glaciofluvial units and 16 radiocarbon ages (∼1.2–8.6  ka) for the alluvial-fan and colluvial units and constrains SM1 and SM2 to 5.5±0.2  ka, 1σ (5.2–5.9 ka, 95%) and 9.7±0.9  ka, 1σ (8.5–11.5 ka, 95%), respectively. Structural, stratigraphic, and geomorphic relations yield vertical displacements for SM1 (2.0±0.6  m, 1σ) and SM2 (2.0±1.0  m, 1σ). The Steamboat Mountain paleoseismic chronology overlaps temporally with earthquakes interpreted from previous terrestrial and lacustrine paleoseismic data along the fault. Integrating these data, we infer that the youngest Teton fault rupture occurred at ∼5.3  ka, generated 1.7±1.0  m, 1σ of vertical displacement along 51–70 km of the fault, and had a moment magnitude (Mw) of ∼7.0–7.2. This rupture was apparently unimpeded by structural complexities along the Teton fault. The integrated chronology permits a previous full-length rupture at ∼10  ka and possible partial ruptures of the fault at ∼8–9  ka. To reconcile conflicting terrestrial and lacustrine paleoseismic data, we propose a hypothesis of alternating full- and partial-length ruptures of the Teton fault, including Mw∼6.5–7.2 earthquakes every ∼1.2  ky. Additional paleoseismic data for the northern and central sections of the fault would serve to test this bimodal rupture hypothesis. 

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3. Slip History, Tectonic Evolution, and Fault Zone Structure Along the Southern Alpine Fault, New Zealand

   https://doi.org/10.1029/2024GC011839  

   Mere, A M; Barth, N C; Schwartz, J J; Kylander‐Clark, A (November 2024, Geochemistry, Geophysics, Geosystems)

   The study of active fault zones is fundamental to understanding both long‐term tectonics and short‐term earthquake behavior. Here, we integrate lidar‐enabled geomorphic‐geologic mapping and petrochronological analysis to reveal the slip‐history, tectonic evolution, and structure of the southern Alpine Fault in New Zealand. New petrographic, zircon U‐Pb and zircon trace‐element data from fault‐displaced basement units provides constraint on ∼70–90 km of right‐lateral displacement on the presently active strand of the southern Alpine Fault, which we infer is of Plio‐Quaternary age. This incremental displacement has accumulated while the offshore part of the fault has evolved within a distributed zone of plate boundary deformation. We hypothesize that pre‐existing faults in the continental crust of the Pacific Plate have been exploited as components of this distributed plate boundary system. Along the onshore southern Alpine Fault, detailed mapping of active fault traces reveals complexity in geomorphic fault expression. Our analysis suggests that the major geomorphic features of the southern Alpine Fault correspond to penetrative fault zone structures. We emphasize the region immediately south of the central‐southern section boundary, where a major extensional stepover and restraining bend are located along‐strike of each other. We infer that this geometry may reflect segmentation of the Alpine Fault between two distinct fault segments. The ends of these proposed segments meet near where several Holocene earthquake ruptures have terminated. Our new constraints on the evolution and structure of the southern Alpine Fault help contribute to improved characterization of the greatest onshore source of earthquake hazard in New Zealand. 

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4. Field Observations of Surface Rupture and Fault Displacement in the 2023 Mw 7.8 Pazarcık, Türkiye Earthquake

   https://doi.org/10.5066/p969bht4  

   Duross, Christopher B; Reitman, Nadine G; Hatem, Alexandra E; Henry, Mason B; Lavrentiadis, Grigorios; Milliner, Chris; Asimaki, Domniki; Karakaş, Melike; Seçen, Bahadir (January 2024, U.S. Geological Survey)

   Field observations of surface rupture extent and fault displacement are critical to improving our understanding of rupture processes in the 6 February 2023 earthquakes in the Kahramanmaraş region of Türkiye. This data release includes two primary datasets depicting the 2023 moment magnitude (Mw) 7.8 Pazarcık, Türkiye earthquake rupture: 1) surface rupture mapping (lines) and 2) measurements of left-lateral and vertical fault displacement (points). These observations were made in the field, northwest of Pazarcık, Türkiye along the East Anatolian (EAF) and Narlı faults between 2 and 11 June 2023. Surface-rupture mapping consists of field observations along a 28-km-long reach of the central EAF and northern 5 km of the Narlı fault that lacked previous remote observations. An additional dataset includes observations of no surface rupture. Displacement data include 68 field observations of left-laterally and vertically displaced natural or cultural features, with 62 measurements along the central EAF and 6 measurements on the Narlı fault. Collectively, these data support scientific and humanitarian response efforts, provide field observations for comparison to remote data, and help improve our understanding of the geologic context of the 2023 Kahramanmaraş region earthquakes.   This database, identified as Field Observations of Surface Rupture and Fault Displacement in the 2023 Mw 7.8 Pazarcık, Türkiye Earthquake, has been approved for release by the U.S. Geological Survey (USGS). Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, the database is released on condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.   Explanation of Data   Surface Rupture Mapping Surface-rupture mapping consists of 18 km of on-the-ground field observations along a 28 km reach of the EAF and the northern 5 km of the Narlı fault recorded using handheld global navigation satellite system (GNSS) devices and tablets. Rupture traces were mapped at a spatial accuracy of ≤10 m and compiled in the office at a scale of 1:1500. Although these data accurately represent the rupture at this scale, additional distributed, cryptic, or small (<0.1 m) displacements not recognized in the field may be present but not depicted in the linework. Linework are available as shapefile, keyhole markup language, and geojson.   Fields: Fault: Fault along which rupture observation was made. EAF – East Anatolian fault.   Date: Calendar date of rupture mapping in format day–month-year.   Notes: Notes on geomorphic expression of rupture. “Null” indicates no additional information reported for rupture trace.   No Surface Rupture This dataset includes line observations of no surface rupture. These data represent areas that we walked during our field campaign, but made no observations of rupture, including distributed zones of cracking or displacement. Although we are confident that no surface rupture with measurable lateral or vertical displacement (exceeding a few centimeters) is present in this area, cryptic or subtle (<0.01 m) displacements not recognized in the field may be present but not depicted in the linework. Linework based on walk tracks mapped at a spatial accuracy of ≤10 m and simplified and compiled in the office at a consistent scale of 1:1500. Linework are available as shapefile, keyhole markup language, and geojson.   Fields: Date: Calendar date of no rupture observation in format day–month-year.   Notes: Notes on whether minor cracking, without measurable lateral or vertical displacement, was observed.   Displacement data Fault displacement data include 68 field observations of left-laterally and vertically displaced natural (e.g., gully thalweg) or cultural (e.g., road edge) features along the EAF and Narlı fault. Left-lateral displacements were measured by projecting sub-linear features into the fault rupture using chaining pins and tape measures. Data were recorded using field notebooks, cameras, tablets, and handheld GNSS devices (≤10 m accuracy) and compiled in the office. Time-averaged GNSS points from tablets and high-precision GNSS (Trimble Geo7x; <1 m accuracy) measured along the features were recorded in the field and used in the office to measure displacement. Descriptions of measurement methods, features evaluated, and displacement values and uncertainties are included in tabular format as comma-separated values (CSV), shapefile, keyhole markup language, and geojson.   Fields: ID: Unique numerical identifier for point observation.   Latitude: Decimal degrees north of the equator; WGS 84, EPSG 4326.   Longitude: Decimal degrees east of the prime meridian; WGS 84, EPSG 4326.   Date. Calendar date of point measurement in format day–month-year.   Fault: Fault along which displacement observation was made. EAF – East Anatolian fault.   H_pref_m: Field-based preferred left-lateral displacement in meters of a natural (e.g., stream channel) or cultural (e.g., concrete wall) feature crossing the fault.   Pref_type: Methods used to determine H_pref_m. Measured – value measured in the field. Sum – value is the sum of separate displacement measurements for subparallel strands (refer to Notes field for description and component displacement values). Midpoint – value is the midpoint between the H_min_m and H_max_m displacement values. Spatial – value measured in the office using spatial data (points) recorded in the field.    H_min_m: Field-based minimum left-lateral displacement in meters of a natural or cultural feature crossing the fault. Approximates lower 95% confidence bound unless otherwise noted.   H_max_m: Field-based maximum left-lateral displacement in meters of a natural (e.g., stream channel) or cultural (e.g., concrete wall) feature crossing the fault.  Approximates upper 95% confidence bound unless otherwise noted.   Aperture_m: Total distance over which features offset by fault rupture are projected to determine displacement across the site. The aperture includes the fault zone and any distributed deformation of the feature.   FaultStrike: Local (m-scale) strike of fault in degrees at displacement measurement site using a 6-degree declination. Measurements without a corresponding dip entry (NaN entry in FaultDip field) reflect the general azimuth of the surface rupture with an estimated uncertainty of ±5 degrees.    FaultDip: Local (m-scale) dip of fault in degrees at displacement measurement site. Dip direction is based on right-hand rule, combined with the corresponding FaultStrike entry for the measurement site.   FeatAzim_N: Azimuth of the faulted cultural or natural feature in degrees (6-degree declination) on the north side of the surface rupture.   FeatAzim_S: Azimuth of the faulted cultural or natural feature in degrees (6-degree declination) on the south side of the surface rupture.   V_pref_m: Field-based preferred scarp height in meters of a natural or cultural feature or surface crossing the fault.    V_min_m: Field-based minimum scarp height in meters of a natural or cultural crossing the fault.  V_min_m approximates lower 95% confidence bound unless otherwise noted.   V_max_m: Field-based maximum scarp height in meters of a natural or cultural feature or surface crossing the fault.  Approximates upper 95% confidence bound unless otherwise noted.   ScarpFaceDir: Facing direction of vertical scarp produced in surface rupture. Variable – variable scarp facing directions are present. None – rupture does not have a vertical expression.   MsmtType: Whether left-lateral or vertical displacements capture slip in all known rupture traces. Complete – measurement captures all recognized and mapped slip at the site; however, the measurement may still lack minor displacement from distributed, far-field, and/or cryptic slip. Incomplete – Some recognized and mapped rupture traces are not accounted for in the displacement measurement (e.g., the feature evaluated only crosses one of two subparallel rupture strands) and is considered a minimum value. Likely complete – the measurement is more likely to be a complete measurement than an incomplete (minimum) estimate. Likely incomplete – the measurement is more likely to be an incomplete (minimum) estimate than a complete measurement.   Setting: General setting of the displacement measurement. Cultural includes built (e.g., rock wall), planted (e.g., orchard rows), or modified (e.g., irrigation ditch) features. Natural indicates erosional or depositional features such as a gully or gravel bar.     Feature: Natural or cultural feature crossing the fault, displaced by the surface rupture, and used to estimate left-lateral and/or vertical displacement.   MsmtMethod: Methods used to measure horizontal displacement. Projection – natural or cultural feature projected into the fault zone using chaining pins and/or tape measures with uncertainty defined by multiple projections. Quick tape – displacement estimated by measuring the distance between piercing points (where linear features crossing the fault intersect the rupture) subparallel to the fault rupture with a tape measure (no projections). Uncertainties measured or estimated. Spatial – points along feature measured using time-averaged Trimble Geo7x or Avenza; displacement measured in office with uncertainties based on multiple projections.   Notes: Description of the feature used to measure displacement, the expression of the rupture (e.g., multiple strands), measurement confidence, and/or information on repeated measurements. Abbreviations: EQ – earthquake; msmt – measurement; N – north; S – south; E – east; W – west; NE – northeast; NW – northwest; SE – southeast; SW – southwest; Geo7x – Trimble Geo7x GNSS device; GEER team – previous measurements made by a Geotechnical Extreme Events Reconnaissance (GEER) team in March 2023.   

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5. A road guide to the Harpeth River and Stones River fault zones on the northwest flank of the Nashville dome, central Tennessee

   https://doi.org/10.1130/2015.0039(01)  

   Abolins, M.; Young, S.; Camacho, M.; Trexler, M.; Ward, A.; Cooley, M.; Ogden, A. (April 2015, Field guide)

   The authors use mesoscale structures and existing 1:24,000 scale geologic maps to infer the locations of four macroscale NNW-striking blind normal faults on the northwest flank of the Nashville dome ~30 km south of downtown Nashville. The Harpeth River fault zone has an across-strike width of ~6 km, and, from west to east, includes the Peytonsville, Arno, McClory Creek, and McDaniel fault zones. All of the fault zones are east-side-down except for the west-side-down Peytonsville fault zone. Mesoscale structures are exposed within each fault zone and are observed at three stops along Tennessee State Route (S.R.)-840 and at an additional stop 1.8 km south of the highway. These structures include minor normal faults (maximum dip separation 3.8 m), non-vertical joints, and mesoscale folds. No faults are depicted on existing geologic maps of the zone, but these maps reveal macroscale folding of the contact between the Ordovician Carters Formation and the overlying Hermitage Formation. The authors use the orientation and amplitude of these folds to constrain the orientation and length of the inferred blind fault zones and the amount of structural relief across the zones. The longest fault zones are the Arno (13.2 km long) and McDaniel (11.6 km) fault zones, and the amount of structural relief across these zones peaks at 27 m and 24 m, respectively. The authors also use existing geologic maps to hypothesize that a second east-side-down blind normal fault zone (Stones River fault zone) is located ~27 km northeast of the Harpeth River fault zone. The authors interpret non-vertical joints at one stop as fault-related, and they interpret joints at a second stop as related to a hanging wall syncline. Both of these stops are within 4 km of S.R.-840. 

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