Recent 230Th dating of fossil corals in west Luzon has provided new insights on the emergence of late Quaternary marine terraces that fringe west Luzon Island facing the Manila Trench. Apart from regional sea level changes, accumulated uplift from aseismic and seismic processes may have influenced the emergence of sea level indicators such as coral terraces and notches. Varied elevations of middle-to-late Holocene coral terraces along the west Luzon coasts reveal the differential uplift that is probably associated with the movement of local onland faults or upper-plate structures across the Manila Trench forearc basin. In Badoc Island, offshore west of Luzon mainland, we found notably young fossil corals, dated at 945.1 ± 4.6 years BP and 903.1 ± 3.9 years BP, on top of a ~5-m-high reef platform. To constrain the mechanism of emergence or emplacement of these fossil corals, we use field geomorphic data and wave inundation models to constrain an extreme wave event that affected west Luzon about 1000 years ago. Our preliminary tectonic and tsunami models show that a megathrust rupture will likely lead to subsidence of a large part of the west Luzon coast, while permanent coastal uplift is attributed to an offshore upper-plate rupture in the northern Manila Trench forearc region. The modeled source fault ruptures and tsunami lead to a maximum wave height of more than 3 m and inundation distance as far as 2 km along the coasts of western and northern Luzon. While emplacement of coral boulders by an unusually strong typhoon is also likely, modeled storm surge heights along west Luzon do not exceed 2 m even with Typhoon Haiyan characteristics. Whether tsunami or unusually strong typhoon, the occurrence of a prehistoric extreme wave event in west Luzon remains an important issue in future studies of coastal hazards in the South China Sea region.

The significance of continental crustal growth in the Phanerozoic has long been debated. As an active accretionary orogenic belt, SE Asia has been proposed to be one of the best archives for studying juvenile continental growth in the Cenozoic, despite the limited availability of data. Therefore, we conducted for the first time a comprehensive U–Pb and Hf isotopic analysis of detrital zircons separated from major rivers of Luzon Island, the largest landmass of the Philippine Archipelago. U–Pb ages of these zircons are predominantly <50 Ma, consistent with literature zircon U–Pb ages or whole-rock K–Ar ages. A sample from the central Sierra Madre, however, contains zircons with age clusters at 110–70 and 180–140 Ma, supporting the presence of Mesozoic basement rock units in that area. All dated zircons show positive and high εHf(T) values that plot close to the depleted mantle. Therefore, we argue that pre-Cenozoic continental materials played insignificant roles in the construction of Luzon Island, and that this part of the southeastern Eurasian margin consists predominantly of a juvenile terrane where substantial continental crustal growth occurred in the Cenozoic. Supplementary material: U–Pb ages and Hf isotopic results for detrital zircons from all samples are available at https://doi.org/10.6084/m9.figshare.c.4481882

The mangroves in Santo Angel in the municipality of Calauag, Quezon Province in the Philippines, provide a wide array of ecological services that range from provisioning of resources and habitat to various floral and faunal species to regulating services including coastal protection. Coastal protection from mangroves is needed by the local community as Santo Angel is susceptible to typhoons and storm surges. However, the mangrove’s ability to provide coastal defense has considerably declined in the past decades due to overexploitation. Using the double-bounded dichotomous choice contingent valuation method, the willingness to pay (WTP) of the local community for a hypothetical mangrove rehabilitation project aligned towards coastal protection was determined. A total of 210 households were involved in the survey. The results show that 79% of the 210 households expressed WTP for the mangrove rehabilitation project. Furthermore, the mean willingness to pay (MWTP) for the mangrove rehabilitation project was computed at Php 15.44 (USD 0.29) per household per month or equivalent to Php 86, 525.76 (USD 1,659.41) per year for the total number of households in Santo Angel. Findings of the logistic regression analysis revealed that sex, age, membership in environmental organizations, and awareness on both the economic importance and the ecological services provided by mangroves positively affect the WTP of the respondents. In contrast, the bid amount and the respondent’s income negatively influence the WTP of the respondents for the mangrove rehabilitation project.