Tephra seismites – understanding seismic hazard of hidden faults by analyzing liquefied tephra layers in lakes

Assessing seismic hazards in regions with hidden or poorly expressed faults is one of the major challenges in paleoseismology today. Here, we utilized CT imaging to quantify the dimensions and distribution of liquefaction structures in ≤17.5-ka old tephra layers in 18 lakes scattered across the poorly expressed Hamilton Basin fault system in northern New Zealand. These ‘tephra seismites’, embedded in unconsolidated, organic-bearing lake sediment, increase in occurrence and dimensions towards known faults and indicate the occurrence of a local hidden fault segment. Through incorporating peak ground acceleration modeling, we found that the spatial distribution of tephra seismites directly relates to the ground shaking induced by near-field fault ruptures. We used the variability in tephra seismites within the stratigraphic record, and tephrochronology, to better constrain the recurrence intervals and magnitudes of paleoearthquakes from both the Hamilton Basin and adjacent Hauraki Basin fa..., , , # Tephra seismites – understanding seismic hazard of hidden faults by analyzing liquefied tephra layers in lakes

Dataset DOI: [10.5061/dryad.5x69p8dj9](https://doi.org/10.5061/dryad.5x69p8dj9)

## Description of the data and file structure

This Zip file contains CT data of sediment cores from the Hamilton lowlands, New Zealand. CT stacks of a total of 60 sediment cores from 18 different lakes are included. The following data processing steps were undertaken.

CT imaging was performed using a medical CT scanner on 60 whole-round cores prior to opening (i.e., all lake cores except HL-A2 and HL-A3 from Rotoroa/Hamilton Lake, which were not available for CT imaging) to visualize and unambiguously quantify tephra layers and soft-sediment deformation structures. The whole-round core was positioned in the center of the CT table, and preliminary scan results of the tephra layers and tephra seismites could be observed in the CT control room (fig. S1AB).

A CT stack (sequence of cross-sectional...