Figure 1.
Index maps and land-level changes from the 2010 Maule earthquake.
a, Plate-tectonic setting of Chilean margin. Arrows indicate convergences between Nazca and South American plates at circa 70 mm yr−1. b, Maule earthquake setting. Epicentre indicated by star, green contours show plate boundary slip (m) (10). Beach sites: Boyeruca* (Bo), Iloca* (Ilo), Pelluhue* (Pe), Lenga (Le), Colcura (Col), Punta Lavapie* (Lv), Llico* (Lli), Las Peñas (LP) and Lebu* (Leb). Land-level change estimated at sites with * plus Cocholhue (Co), Chome (Cho), Maule (Ma), Isla Santa María (ISM), Quidico (Qui), Tirúa (Tir) and Isla Mocha (IMo) (Table S2). c, Geographic variability in estimated land-level changes (means ±1 standard deviation). Black dot denotes coseismic subsidence at permanent GPS site CONT [51]; black diamonds are estimates of subsidence based on drowned coastlines.
Figure 2.
Beach characteristics as a function of land-level changes.
a–d, Photos of study sites taken before and after the 2010 Maule earthquake. Orange dotted lines indicate 24 hour spring high tide line; a–b, unarmoured sites: a, subsidence (narrower): Boyeruca, b, coastal uplift (wider): Lebu, c–d, armoured sites: c, seawall with uplifted wider intertidal: Punta Lavapie, d, revetment with uplifted wider intertidal: Llico. Note that dry sand areas above high tide line decreased at subsided beaches (a) and increased at uplifted beaches (b, c and d), e–f, Relationships between the magnitude of land-level changes and e, beach widths and f, beach face slopes for sites with seawalls (red dots), sites with rocky revetments (blue dots) and unarmoured sites (black dots). Only statistically significant regressions are shown.
Figure 3.
Responses of sandy beach macrofauna to the 2010 Maule earthquake.
a, subsided beaches, b, beaches with <1.0 m uplift, c, beaches with 2 m uplift. Mean abundance (+1 standard error) of mobile crustaceans representing upper, mid and lower intertidal zones for before (white bars) and after (grey bars) the Maule earthquake at sites located seaward of seawalls (Sw) and rocky revetments (R), and at unarmoured sites (Un). Shaded rectangles over bars indicate: significant decrease (yellow), disappearance (red), significant increase (light blue) and first appearance of species at a site (purple). The three intertidal zones are represented by 1) the talitrid amphipod Orchestoidea tuberculata (upper), 2) the cirolanid isopods Excirolana braziliensis and Excirolana hirsuticauda (mid) and 3) the sand crab Emerita analoga (lower) as illustrated on the figure. Abundances are presented as individuals m−1 to accommodate beach width changes; trends for individuals m−2 were similar except three cases indicated by *. Note: low intertidal seaward of the seawall at Boyeruca was bedrock before and after the earthquake, excluding Emerita analoga, and the beach at Punta Lavapie is completely armoured with a seawall. Numbers below the names of sites on the right side of the figure indicate land-level changes and tsunami heights in meters (m/m, respectively) for each study beach.
Figure 4.
Responses of sandy beach macrofauna to uplift and coastal armouring over time.
Temporal patterns in population abundance of crustaceans from the three intertidal zones listed in Fig. 3 for armoured sites that experienced different amounts of interaction between the structure and local waves and tides before the 2010 earthquake and tsunami, and for unarmoured sites. Mean values (+1 standard error) of abundance before the event are indicated by black bars, mean values of post-event abundance for armoured sites are grey bars and unarmoured sites are white bars. Strength of pre-event armouring and wave interaction (see Methods) increases from left to right as indicated by the grey arrow at the top of the figure. Data are presented as individuals m−1 to accommodate changes in beach widths; trends for individuals m−2 were similar.
Figure 5.
Dead sand crabs, Emerita analoga, stranded in life position at the upper-shore levels of the armoured site at Lebu, illustrate the direct mortality of a dominant lower intertidal invertebrate species observed immediately after the Maule earthquake and tsunami.