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The Philippines has conducted several landslide hazard susceptibility mapping over the past years to increase the requirement for vulnerability assessment. As a karstic mountainous region in the country, the southeast Bohol province is accustomed to frequent landslide occurrences, causing hazard risks in adjacent communities. These landslides are generally controlled by both extrinsic (e.g., road network, fault) and intrinsic (e.g., geomorphologic and geologic) factors. Field observation denotes several occurrences along steep slopes and stream banks. However, challenges in updating the landslide hazard susceptibility maps arose from the scarcity of updated field information and high-precision digital elevation models. With data access limitations, this study aims to generate accurate and precise landslide susceptibility models using remote sensing and statistical-based analysis processed in Geographic Information System (GIS). This study uses open-sourced medium-resolution satellite data and digital elevation models to generate and process the eight (8) landslide factor maps such as the geology, slope gradient, aspect, vegetation, proximity to stream and road networks, soil cover, and fault. These maps were analyzed through Analytical Hierarchy Process (AHP) and Fuzzy Logic Overlay. The generated landslide susceptibility models were validated using Forest-based Classification and Regression (FBCR), analysis of variance (ANOVA), and ordinary linear regression. The AHP-based model shows significant accuracy and compatibility with the actual susceptibility of the site since the p-value of the map is 0.031 in ANOVA, while the Fuzzy-based model cannot be considered accurate since it generated a 0.266 p-value result. Moreover, both models were analyzed in FBCR and resulted in a p-value of 2.2x10− 16 in the ordinary linear regression validation, making both as significant landslide prediction models. This result signifies that medium-resolution satellite data can generate accurate and compatible landslide susceptibility and prediction models, and this process will give disaster risk reduction managers an avenue to generate landslide models that are not bounded by data access limitations. It is also noteworthy to indicate the impact of changing climate in the Philippines where extreme cyclones have been frequent for the past years. Such events contribute to the occurrences of slope and river bank erosion and water saturation to the slope causing the periodic distribution of landslides throughout the study area.

Objective The purpose of this study was to determine the reliability of a comprehensive worksite-level assessment and identify which worksite wellness best practices were implemented following a workshop. Methods Kansas worksites attended a WorkWell Kansas Phase I workshop from 2012 through 2014 and completed a 155-item assessment before the workshop and 1 year later. Cronbach alpha measured the internal consistency of the WorkWell KS Phase I Assessment, and McNemar test assessed differences in proportions from baseline to follow-up. Results Two hundred eighty five worksites completed a baseline assessment, of which, 109 completed the follow-up assessment (32%). The internal consistency of the instrument was 0.96, and worksites reported significant improvements at follow-up from baseline for nine variables. Conclusions Improvements predominantly included creating a wellness committee, assessing needs, and developing goals. There was a lack of policy and systems level improvements at the worksite.

TAIGER project deep-penetration seismic reflection profiles acquired in the northeastern South China Sea (SCS) provide a detailed view of the crustal structure of a very wide rifted continental margin. These profiles document a failed rift zone proximal to the shelf, a zone of thicker crust 150 km from the shelf, and gradually thinning crust toward the COB, spanning a total distance of 250–300 km. Such an expanse of extended continental crust is not unique but it is uncommon for continental margins. We use the high-quality images from this data set to identify the styles of upper and lower crustal structure and how they have thinned in response to extension and, in turn, what rheological variations are predicted that allow for protracted crustal extension. Upper crustal thinning is greatest at the failed rift (βuc ≈ 7.5) but is limited farther seaward (βuc ≈ 1–2). We interpret that the lower crust has discordantly thinned from an original 15–17 km to possibly less than 2–3 km thick beneath the central thick crust zone and more distal areas. This extreme lower crustal thinning indicates that it acted as a weak layer allowing decoupling between the upper crust and the mantle lithosphere. The observed upper crustal thickness variations and implied rheology (lower crustal flow) are consistent with large-scale boudinage of continental crust during protracted extension.

We present a new travel time tomography velocity model and seismic reflection images that delineate the rift architecture and magmatic features of the rifted margin in the northeastern South China Sea. These data reveal moderately stretched crust ~25 km thick along the continental shelf and thin but laterally variable crustal thickness in the distal margin. Along the continental slope, crust rapidly thins to ~4 km in a basin characterized by tilted fault blocks that sole into a low-angle detachment. Strain was localized to a degree within the highly stretched basin but failed to progress to breakup and seafloor spreading. Crust in the distal margin is ~12–15 km thick. Few extensional structures are apparent in the distal margin, but seismic velocities are suggestive of highly thinned and magmatically intruded continental crust. The magmatic features we interpret include volcanic zones at the top of the basement that deform or disrupt overlying postrift strata, sills intruded into the postrift sedimentary section, and a high-velocity (~6.9–7.5 km/s) lower crustal layer that we take to be magmatic underplating or pervasive lower crustal intrusions. These features primarily occur in the distal margin and may have been emplaced during postrift seafloor spreading. The postrift magmatism may have been induced by convective removal of continental lithosphere following breakup and the onset of seafloor spreading in the South China Sea.

[1] We use offshore multichannel seismic (MCS) reflection and wide-angle seismic data sets to model the velocity structure of the incipient arc-continent collision along two trench perpendicular transects in the Bashi Strait between Taiwan and Luzon. This area represents a transition from a tectonic regime dominated by subduction of oceanic crust of the South China Sea, west of the Philippines, to one dominated by subduction and eventual collision of rifted Chinese continental crust with the Luzon volcanic arc culminating in the Taiwan orogeny. The new seismic velocity models show evidence for extended to hyperextended continental crust, ~10–15 km thick, subducting along the Manila trench at 20.5°N along transect T1, as well as evidence indicating that this thinned continental crust is being structurally underplated to the accretionary prism at 21.5°N along transect T2, but not along T1 to the south. Coincident MCS reflection imaging shows highly stretched and faulted crust west of the trench along both transects and what appears to be a midcrustal detachment along transect T2, a potential zone of weakness that may be exploited by accretionary processes during subduction. An additional seismic reflection transect south of T1 shows subduction of normal ocean crust at the Manila trench.

Seismic reflection and wide-angle data acquired across, south, and west of Taiwan show that extended to hyper-extended continental crust of the Chinese continental margin is present more than 200 km south of the shelf and is subducting at the Manila Trench. Furthermore, crustal-scale tomographic velocity models show that this crust is underthrusted to ∼15 km depth below the accretionary prism, where it then is structurally underplated to the base of the prism. We document an increasing volume of accreted crust from south to north, and in our northern transect high-velocity material of the accretionary prism can be directly linked to outcrops of Central Range basement rocks. In map view the Central Range of Taiwan is clearly contiguous with the Hengchun Peninsula and Hengchun submarine ridge to the south. Accordingly, we propose a new model in which the Central Range forms directly from the accretionary prism, including the basement core, which originates from subducted, and then accreted, extended to hyper-extended continental crust.

New marine seismic reflection and coincident wide-angle ocean-bottom seismometer data acquired offshore Taiwan provide high-resolution constraints on the crustal structure of an incipient mountain belt during the earliest stage of arc–continent collision. The new seismic reflection image and travel-time tomography velocity model show evidence for crust of the distal southern Chinese continental margin being subducted eastward beneath the Manila trench and underplated to the accretionary wedge before collision with the southern Chinese continental shelf. The distal margin crust consists of highly extended continental crust interspersed with volcanic bodies and a high-velocity lower crustal layer of likely magmatic intrusions. The distal margin crust is 10–14 km thick outboard of the trench, but thins to 6 km thick beneath the lower slope of the Manila trench accretionary wedge. Along the lower slope of the accretionary prism, we image westward-verging imbricate thrusts and folded strata up to 10 km thick. A sharp decrease in bathymetry marks the transition from lower to upper slope, where we observe a fast (>6.0 km/s) seismic velocity anomaly at the base of the wedge that we interpret as structurally underplated crust from the distal continental margin. Our results support a model of arc–continent collision in Taiwan where the accretionary wedge is first thickened by structural underplating of distal margin crust prior to collision with the continental shelf. The crustal rocks exposed throughout the Central Range in Taiwan may be similarly derived from subducted and structurally underplated crust from the highly extended distal continental margin.

Recent multichannel seismic reflection data acquired offshore southwest Taiwan identify active extension along a deep-seated normal fault in the precollision setting of the Taiwan arc-continent collision. While ubiquitous minor flexural faulting may be observed in the Taiwan foreland, these new data image a listric, rift basin–bounding normal fault that penetrates deep into the crust and forms a significant fault scarp with ∼850 m of relief near the continental shelf break southwest of the Taiwan collision zone. These observations, along with new geodynamic models of collision between a subduction zone and a young passive margin, indicate that the recent extension may be the expression of plate bending in continental crust as thin transitional crust subducts at the Manila Trench. A similar extensional episode prior to the onset of arc-continent collision ca. 6.7 Ma has been identified in rift basins of the southern Chinese margin near Taiwan, further suggesting that collision may be preceded by bending-related extension of the continental shelf. The Lishan fault, a major structural and morphologic boundary in the Taiwan orogen, may have been a similar rift basin–bounding fault before being reactivated during the Taiwan arc-continent collision. In this scenario, the Lishan fault divides Taiwan into a western domain representing collision of the thick crust of the continental shelf and an eastern domain representing subduction and collision of thin transitional crust along the continental slope with the Manila Trench.

During summer of 2009, multi-channel marine seismic reflection data and wide-angle refraction data were acquired as part of the joint NSF and Taiwanese-funded TAIGER program with the goal of understanding the dynamics of arc-continent collision in Taiwan. One of the principle difficulties of crustal-scale imaging with marine reflection data such as these is the prevalent multiple contamination that obscures many of the deep crustal targets. Without effective treatment of multiples, many of the objectives of the TAIGER active source program may not be achieved. We present three profiles, one from each acquisition leg, that demonstrate the effectiveness of 2D surface-related multiple elimination (SRME) and radon filtering in attenuating much of this unwanted energy in broad ranges of water depths, seafloor topographies and lithologies. Two profiles from south of Taiwan image 3–4 km of sedimentary strata overlying moderately extended continental crust along the Eurasia continental shelf and a 5–6 km thick sedimentary section overlying thin crust consisting of faulted blocks and volcanic bodies along the continental slope. Our multiple attenuation efforts also reveal a seaward-dipping normal fault that penetrates into the upper mantle and separates thick crust of the continental shelf from thin crust of the continental slope. A profile from east of Taiwan reveals thin ocean crust of the Philippine Sea plate subducting beneath the Ryukyu trench that may be traced beneath the accretionary prism and Ryukyu forearc. These profiles demonstrate the success of our imaging strategy in the range of imaging environments spanned by the TAIGER marine reflection seismic data.

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