This grading of epitaxial layer may be done in several approaches such as linear or nonlinear grading, step-grading, grading with overshoot interfaces, and reverse grading [23, 24, 25, 26, 27, 28].
The most common combination is a lower part composed of plane or cross laminated sands, reverse graded sands or of massive sediments and an upper part composed of normally graded sediments.
Chigira et al. (2010) and Dai et al. (2011) observed reverse grading on the fan, indicating that valley fill sediments were mobilized by pore pressure build up or liquefaction. .
Normal grading is often reported for tsunami deposits (e.g. Shi et al. 1995; Bondevik et al. 1997b; Minoura et al. 1997; Gelfenbaum and Jaffe 2003), especially in their upper part, reverse graded or ungraded material is typical of the lower part of tsunami deposits but is less common than normal grading (Hori et al. 2007; Paris et al. 2007; Choowong et al. 2008).
Regardless of the number of layers, certain beds may be massive in structure (Fig. 2(C, F)), may reveal normal grading (fining upwards) (Fig. 5), reverse grading, plane parallel lamination (Fig. 2(A, B, D)), crossbedding (Fig. 2(D)), and scour and fill structures.
(2) Normal grading > reverse grading.
A reverse grading is found only in 2 trenches located less than 200 m from the shoreline, forming the lowermost part of the tsunami deposits.
During the transportation process, grain separation can occur, potentially resulting in the formation of normal and/or reverse grading structures in marine tephra beds.
For the fabrication of a virtual substrate with SiGe buffer layers, a method using a reverse grading by a two-step growth procedure was employed [16].
The unit is characterized by matrix-supported texture and weak normal and/or reverse grading in the proximal area; however, the grading structure becomes unclear with distance from the vent.
