Beach ridge patterns in West Aceh, Indonesia, and their response to large earthquakes along the northern Sunda trench

Holocene evolution of Phra Thong's beach-ridge plain (Thailand) — Chronology, processes and driving factors

“…Average shoreline progradation on Phra Thong has a similar dimension as values published elsewhere (e.g., 0.5-3.1 m/year: Clemmensen et al, 2012;1 m/year: Tanner, 1995; 1-2 m/year: Monecke et al, 2015), but there are striking spatial and temporal variations within the ridge plain. Ignoring minor spatial variability, shoreline progradation can be divided into at least two major time periods: (i) between~3300 and~5500 years ago (A 1 , F 1 , F 2 and possibly A 2 and C 1 as well) the development is characterised by high progradation rates of 2.1-2.7 m/year; and (ii) from~3300 years ago to the present, progradation slowed down to rates of 0.7-0.87 m/year (E 1 , E 2 , B 1 , C 2 and C 3 ).…”

“…Decadal to centennial sea-level variations that in theory could explain the observed ridge-and swale formation on Phra Thong (Tanner, 1995) have indeed been documented in SW Thailand as a result of plate rebound connected to tectonics at the Sunda Arc (Trisirisatayawong et al, 2011). However, different from the Aceh coast of Sumatra (Monecke et al, 2015) the formation of a prominent swale could not be observed after the relative sea-level change related to the IOT 2004. A better explanation for the recurrence of ridge sets and ridge-swale successions therefore is the observed interaction of beach erosion and ridge accretion during tsunamis and storms that has been identified as the most likely mechanism in other subtropical ridge plains (e.g., Nott et al, 2009).…”

“…Thus, they may result from (i) the swash of fair-weather swell waves; (ii) the run-up of storm waves; or (iii) the influence of longshore transport (Woodroffe, 2002: 293;Tamura, 2012). Ridge formation during single extreme events can be excluded on Phra Thong Island, because both land-falling storms and tsunamis, rather lead to erosion of the shoreline as documented for the Indian Ocean Tsunami in 2004 (e.g., Choowong et al, 2007;Kelletat et al, 2007;Monecke et al, 2015) and summer storms in 2013 and 2014 (own observations from December 2013 and eyewitness reports of local residents). However, erosion by storms and tsunamis was restricted to the beach zone terminating with an erosive scarp at the seaward side of the youngest beach ridge (Fig.…”

“…This includes reconstruction of coastal evolution (e.g., Dominguez et al, 1987;Anthony, 1995;Roberts and Plater, 2007;Tamura et al, 2008;Clemmensen et al, 2012), variations in cyclone activity (e.g., Nott, 2011;May et al, 2013), changes in sea level (e.g., Goy et al, 2003;Schellmann and Radtke, 2010), palaeooceanography (Brückner et al, 2002;Brückner and Schellmann, 2003), co-seismic uplift or subsidence (Monecke et al, 2015), or climate variability (Sandweiss, 1986;Brooke et al, 2008). Although many of these studies demonstrate that beach ridges can effectively be used to successfully reconstruct the processes and driving factors of their formation, site-dependent and often complex interactions of different formation processes require temporal and spatial resolution that is sufficient to unravel this complexity.…”

Beach ridges as paleoseismic indicators of abrupt coastal subsidence during subduction zone earthquakes, and implications for Alaska-Aleutian subduction zone paleoseismology, southeast coast of the Kenai Peninsula, Alaska

“…Data sources: Briggs et al, 2014;Shennan et al, 2014a;2014b;2014c;Shennan, 2009;Shennan et al, 2009;Freymueller et al, 2008;Zweck et al, 2002;Mann and Crowell, 1996;Plafker, 1969. coseismic, relative sea-level change; but these sites have in common a high wave energy coast and, at the location of beach ridges, no fluvial sediment input to the coast. Monecke et al (2015) show that coseismic subsidence from the 2004 AndamaneAceh earthquake triggered erosion of the active beach ridge on the south Aceh coast and rebuilding of a new beach ridge in the following few years. But the south Aceh coast is a sediment-supply-rich system, and other mechanisms besides coseismic subsidence may form, and preserve, beach ridges.…”