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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.   

Seismic hazard in Mexico City governed by site effects. The M8.1 1985 subduction zone earthquake, which caused significant damage and loss of thousands of lives at 350 km epicentral distance, has become the quintessential example of the role that site effects can play in modifying the amplitude, frequency, and duration of ground shaking; and in aggravating the catastrophic consequences of earthquakes. We here present observations and analyses of the M7.1 September 19, 2017, event that—while triggered by an intraplate rupture at approximately half the epicentral distance of the 1985 event relative to Mexico City—caused severe structural damage to a few tens of buildings located in a relatively narrow zone between the hill and lake zones of the basin, known as the transition zone. We show that the M 7.1 mainshock exposed the vulnerabilities of the pre-1985 building code in the transition zone; but more importantly highlighted the improvement of the 1987 building code revision in terms of the performance of modern high-rise buildings that suffered catastrophic consequences during the 1985 Michoácan earthquake sequence. We next analyze several records collected at stations in the basin over the past 20 years. We highlight the importance of three-dimensional heterogeneity of the basin sediments, the coupling between hydrological setting and site response and their evolution with time, and the energy interaction between the deep basin edge and the shallow clay layers. Results presented are the collective effort of the GEER teams that were deployed to perform post-earthquake reconnaissance in the affected regions of the epicentral area and in Mexico City after the M 7.1 September 19, 2017, earthquake sequence.