Sub-surface shear wave velocity models developed based on a combined in-situ measurement of quasi-static cone penetration test (q-CPT) and microtremor datasets.

A representative sub-surface shear wave velocity model is crucial for seismic hazard studies, as seismic waves are affected by sub-surface characteristics. The offered data in this article were mainly developed based on a quasi-static cone penetration test (q-CPT) collected at the west coast town of Aceh, Indonesia. Microtremor datasets measured at the same locations were employed to extend the depth of the sub-surface models and to validate the models. The in-situ q-CPT data were collected using a locally manufactured Begemann's type cone penetration test apparatus. Twenty seven (27) q-CPT soundings were performed to typical depths of 20 m or measuring cone tip resistances of at least 150 kg/cm2. Several empirical approaches were employed to deduce the sub-surface parameters, including shear wave velocity. To enhance the sub-surface model depth, 23 in-situ microtremor data were recorded using 3 components (3C) of Geobit S100 and RaspberrySHAKE (RS-3D) seismometers at the same locations where the q-CPTs were sounded. At the same time, these microtremor datasets were also utilized to validate the developed sub-surface shear wave velocity models using the forward modeling method. Therefore, all the proposed sub-surface shear wave models presented in this article have been validated. These sub-surface shear wave velocity models can be used for site characterization, i.e., site response analysis, seismic microzonation, or spatial urban planning.

The Effects of Nanosilica on Mechanical Properties and Fracture Toughness of Geopolymer Cement.

Nanosilica produced from physically-processed white rice husk ash agricultural waste can be incorporated into geopolymer cement-based materials to improve the mechanical and micro performance. This study aimed to investigate the effect of natural nanosilica on the mechanical properties and microstructure of geopolymer cement. It examined the mechanical behavior of geopolymer paste reinforced with 2, 3, and 4 wt% nanosilica. The tests of compressive strength, direct tensile strength, three bending tests, Scanning Electron Microscope-Energy Dispersive X-ray (SEM/EDX), X-ray Diffraction (XRD), and Fourier-transform Infrared Spectroscopy (FTIR) were undertaken to evaluate the effect of nanosilica addition to the geopolymer paste. The addition of 2 wt% nanosilica in the geopolymer paste increased the compressive strength by 22%, flexural strength by 82%, and fracture toughness by 82% but decreased the direct tensile strength by 31%. The microstructure analysis using SEM, XRD, and FTIR showed the formation of calcium alumina-silicate hydrate (C-A-S-H) gel. The SEM images also revealed a compact and cohesive geopolymer matrix, indicating that the mechanical properties of geopolymers with 2 wt% nanosilica were improved. Thus, it is feasible for nanosilica to be used as a binder.

Microtremor datasets at liquefaction site of Petobo, Central Sulawesi-Indonesia.

The liquefaction at Petobo, Central Sulawesi affected at least 1.8 square kilometers, destroyed up to 744 houses, and caused more than 104 casualties. The data offered in this article are microtremor measurement datasets at the liquefaction site of Petobo, Central Sulawesi, Indonesia. The datasets were recorded using 3 component (3C) Guralp 6T-D broadband seismometer. There are 14 microtremor datasets, which consist of 10 datasets measured inside the liquefaction affected site and 4 datasets recorded outside the liquefaction affected site of Petobo, Central Sulawesi. Two to four datasets with 20 min length, were recorded at different times at each location. The microtremor data is crucial for horizontal to vertical (H/V) spectral ratio analysis, from which both the fundamental frequency and ellipticity curve at the measured site are deduced. The site fundamental frequency is useful for estimating the characteristics of the sub-surface condition at the measured site. The curve of the Rayleigh waves fundamental mode is needed to develop the shear wave (S-wave) velocity profile of the measured site.