Are Field Observations of Surface Rupture Useful? An Example from the 2023 Mw 7.8 Pazarcık, Turkey (Türkiye), Earthquake

Abstract Field investigations have long been an important component of the scientific response to surface-faulting earthquakes. However, in light of advances in remote data and models, the question arises whether field-based observations of surface rupture remain useful for understanding rupture processes and seismic hazards. We approach this question using a field-based study of the central 2023 Mw 7.8 Pazarcık, Turkey (Türkiye), earthquake rupture, at the intersection of the east Anatolian fault (EAF) and Narlı fault. Our field observations include the surface rupture expression and extent of the central EAF and northernmost Narlı fault in generally forested and steep terrain and 68 measurements of left-lateral surface displacement. These data improve our understanding of the Pazarcık rupture complexity, resolve the surface geometry of the Narlı fault–EAF connection, and exhibit a clear (>2 m) change in surface displacement across this intersection zone that confirms remote-based coseismic slip models. Our study shows that focusing field efforts in areas of obscured or low-resolution remote data can yield essential data for refining rupture extent, documenting perishable on-fault displacement, and improving postearthquake situational awareness. A comparison of similarly large-magnitude continental surface-rupturing earthquakes indicates that displacement uncertainties relate to a complex set of factors, including measurement methods, rupture complexity, and displacement magnitude. Our study validates the need for postearthquake field observations, which, when driven by clear motivating questions and knowledge of methodological strengths and limitations, provide high-resolution rupture data that complement remote-based models.