Abstract
The importance of small-scale seismic events in enclosed water bodies, which can result in large tsunami waves capable of affecting comprehensive damage over small, geographically-confined areas are generally overlooked, although recognizing the occurrence of such events is a necessary element in adequately assessing the risk of natural hazards at specific locations. Here we present evidence for a probable large localized tsunami that occurred within the Bay of La Paz, Baja California Sur, ~1100 year before present (BP), which resulted in the creation of a shelly ridge at an elevation of ~2 m above mean high water (MHW). This ridge consists of a continuous wedge of poorly mixed marine sands and shells ~50 cm in depth deposited along the entire seaward edge of the lake. The marine shells collected from terrestrial environments around the lake include species from a variety of environments, including offshore species with minimum preferred depths of >13 m. The evidence suggests that this material was likely deposited by a tsunami with a runup of 2–3.6 m above MHW, probably associated with the slumping of an island along the tectonically active eastern edge of the bay.
Highlights
Two recent events have focused attention on the hazards associated with supra-regional tsunamis generated by mega earthquakes occurring along major fault lines in the open ocean
One example is the 1958 Lituya Bay, Alaska tsunami. This event was associated with a large earthquake on the Fairweather Fault, the proximal cause was a rockslide at the head of the bay that generated a tsunami that removed soil and vegetation up to a height of 524 m [7]
Examples include Crassotrea that commonly occur in back bays, Chione californiensis and Chionista fluctifraga that inhabit intertidal and nearshore areas, offshore species, and coral fragments (Table 1, Figure 4)
Summary
Two recent events have focused attention on the hazards associated with supra-regional tsunamis generated by mega earthquakes occurring along major fault lines in the open ocean. The ensuing tsunami, that generated waves up to 30 m high, caused over 283,000 deaths in 14 countries [1,2]. On 11 March 2011, a 9.0 magnitude earthquake associated with a 450 km rupture of the Japan Trench generated a tsunami [3,4] that devastated Japan and achieved wave heights of 3.94 m as distant as the southern coast of Chile [5]. One example is the 1958 Lituya Bay, Alaska tsunami. This event was associated with a large earthquake on the Fairweather Fault, the proximal cause was a rockslide at the head of the bay that generated a tsunami that removed soil and vegetation up to a height of 524 m [7].
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