**2.2 Itrax data and analysis**

Itrax XRF involves the excitation of a sample by X-rays using either a molybdenum (Mo) or chromium (Cr) anode X-ray tube, causing the sample to fluoresce. That is, the sample emits secondary X-rays that are distinctive of the elements which they were emitted from. The relative intensity of these fluorescent signals provides an indication of the elemental composition of the sample [9, 10]. The Motube is commonly used in most applications and is more appropriate for detecting heavier elements, while the Cr- tube more adequately detects lighter elements. For example, Al and Si. Nevertheless, an X-ray exposure time of approximately 10–20 s on the sample using a Mo- tube and the Itrax Q-spec procedure is adequate for obtaining acceptable data for these light elements [10].

Itrax elemental data used in this study were initially presented in [19] and were obtained in 2012 using the Itrax core scanner at the Australian Nuclear Science and Technology Organisation (ANSTO). The scanner was fitted with a Mo- tube and a magnetic susceptibility meter, with XRF scans performed on each core at 30 kV and 55 mA using 10 s exposure time and sampled at 500 μm step size. In comparison, Itrax analysis of the Little Pigeon Bay cores were carried out using similar settings at the University of Auckland [8], with a negligible difference of 4 s exposure time between the two datasets [20].

The samples were air dried and the surfaces cleaned to minimize water content and matrix effects in the core prior to analysis. Data quality was ensured through normalization against the Al detected for each core, with profile gaps resolved through interpolation by a moving average curve. This enabled more meaningful trends to be observed in the core sequences. Identified elevated elemental signals relative to adjacent units were compared for consistency with detected changes in unit stratigraphy, grain size, loss on ignition (indicative of organic content if the changes are greater than 5%), and pXRF results for these cores, provided in [19].

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**Figure 2.**

*provide tentative benchmarks for interpretation.*

*Tsunami Elemental Signatures in the Samoan Islands: A Case Study*

Normalized data was used to identify distinct elevated elemental signals in the core profiles comparable to benchmark tsunami signatures provided in [8]. Elevated signals at the surfaces of the Ma'asina and Manono cores are particularly screened for benchmark signatures indicative of the 2009 tsunami. Identified elevated elemental units are compared with descriptions of sites, core stratigraphies, and analogue tsunami deposits of the 2009 tsunami in [16, 19], to interpret

The Samoan cores show comparable elemental profile trends to those observed at Little Pigeon Bay when normalized against Al (**Figure 2**). At Little Pigeon Bay, a sharp sedimentary contact denoted by distinct elevations in elemental levels

*Selected Itrax data (normalized over Al) for profiles S1 (Ma'asina), S2 (Manono-uta) and S3 (Lano). Time markers shown at Ma'asina are based on 210Pb constant initial concentration (CIC) and constant rate of supply (CRS) ages up to 11 cm profile depth provided in [19] and are forecast using a power function curve. Calibrated 14C age shown at Lano was sourced from [19]. All time markers presented are indicative only and* 

*DOI: http://dx.doi.org/10.5772/intechopen.85639*

distinct tsunami episodes in the core profiles.

**2.3 Tsunami deposit identification**

**3. Results and interpretations**

*Tsunami Elemental Signatures in the Samoan Islands: A Case Study DOI: http://dx.doi.org/10.5772/intechopen.85639*
