Grain imbrication analysis of tsunami deposits using statistical hypothesis testing

Identifying run-up and backwash units from sediments is important to distinguish tsunami deposits from layers formed by other events such as river floods. To reconstruct run-up and backwash of past tsunami, we conducted grain imbrication analysis using statistical hypothesis testing on X-ray computed tomography (CT) images of a gravelly tsunami deposit. Grain imbrication analysis was conducted on the gravel in a layer namely S1. Three cores taken at 2 sites were used for the analysis. The results were shown as rose diagrams, then we conducted statistical hypothesis testing to examine the distribution patterns of the angle data of the grain imbrication. Grain imbrication analysis and statistical hypothesis testing revealed a run-up and a backwash units in the layer S1. Units of run-up in the layer S1 are thicker and more frequently observed than units of backwash.