Luminescence sediment tracing reveals the complex dynamics of colluvial wedge formation

Abstract

Paleoearthquake studies that inform seismic hazard rely on assumptions of sediment transport that remain largely untested. Here, we test a widespread conceptual model and a new numerical model on the formation of colluvial wedges, a key deposit used to constrain the timing of paleoearthquakes. We perform this test by applying luminescence, a sunlight-sensitive sediment tracer, at a field site displaying classic colluvial wedge morphostratigraphy. The model and data comparison reveals complex sediment transport processes beyond the predictions of either conceptual or numerical models, including periods of simultaneous debris and wash facies forming processes, erosion, and reworking. These processes could lead to preservation bias, such as incomplete or overinterpretable paleoearthquake records, given the right environmental conditions. Attention to the site-specific mechanics of fault zone depositional systems, such as via sediment tracing, may buffer against the possible effects of preservation bias on paleoseismic study.

Landscape domains and information surfaces: Data collection, recording and citation using decimal latitude‐longitude geolocation via the FAIR principles

“…Topographic landscapes, especially regarding modelling approaches (diffusional, CA and non-local), sites will benefit from dLLspecified site references and with the ability of points to be considered in Eulerian or Lagrangian reference systems. For example, Gray et al (2022) have recently used a dLL (although not in the tuple format) to specify an investigated fault-scarp site on a hillslope. The AGU 'Landslide Blog' (Petley, 2023) Although the dLL information in most citation-references is lacking (as noted previously in the periglacial landscape book and the previous example), this does not mean that it cannot be added retrospectively or used to provide access to new information.…”