Earthquake disasters can have a serious impact on people’s lives and property, with damage to buildings being one of the main causes of death and injury. A rapid assessment of the extent of building damage is essential for emergency response management, rescue operations, and reconstruction. Terrestrial laser scanning technology can obtain high precision light detection and ranging (LiDAR) point cloud data of the target. The technology is widely used in various fields; however, the quantitative analysis of building seismic information is the focus and difficulty of ground-based LiDAR data analysis processing. This paper takes full advantage of the high-precision characteristics of ground-based LiDAR data. A triangular network vector model (TIN-shaped model) was created in conjunction with the alpha shapes algorithm, solving the problem of small, nonvisually identifiable postearthquake building damage feature extraction bias. The model measures the length, width, and depth of building cracks, extracts the amount of wall tilt deformation, and labels the deformation zone. The creation of this model can provide scientific basis and technical support for postearthquake emergency relief, assessment of damage to buildings, extraction of deformation characteristics of other structures (bridges, tunnels, dams, etc.), and seismic reinforcement of buildings. The research data in this paper were collected by the author’s research team in the first time after the 2013 Lushan earthquake and is one of the few sets of foundation of LiDAR data covering the full range of postearthquake building types in the region, with the data information mainly including different damage levels of different structural types of buildings. The modeling analysis of this data provides a scientific basis for establishing the earthquake damage matrix of buildings in the region.
The rapid assessment of an intensity map following a strong earthquake forms the foundation for risk assessment and emergency response in Chinese mainland. The determination of the major axis direction in the assessed intensity map depends on various factors, including nearby active faults, instrumental intensities, and the distribution of aftershocks. To evaluate the effectiveness of promptly determining the major axis direction based on early aftershock distribution, we relocated and analyzed aftershock sequences occurring within 2 h of eighteen aftershock-rich earthquakes with a magnitude of Ms ≥ 6.0 in Chinese mainland from 2012 to 2021. HypoDD was used for relocation, and the standard deviational ellipse fitting technique was employed for analysis. Comparing the aftershock ellipses resulting from our analysis with the macroseismic intensity maps obtained from field surveys reveals a high level of agreement, with an average difference of approximately 9° in the major axis directions of the aftershock ellipses and the meizoseismal zones. For the majority of earthquakes, regardless of focal mechanisms, the lengths of the major axes of the aftershock ellipses closely correspond to the intensity VIII scale. Additionally, the spatial distribution of aftershocks aids in distinguishing the seismogenic fault from the two fault planes with distinctly different dips as indicated by the focal mechanism solution. Moreover, the distance between the aftershock center and the macroseismic epicenter systematically increases as the dip decreases. These findings hold significant scientific value as they contribute to the prompt determination of assessed intensity maps and provide effective guidance for earthquake emergency response.
in order to enhance the separation performance and to reduce the heat loss of the transmembrane for membrane distillation, the thermal efficiency and hydrophobicity of the membrane distillation should be simultaneously enhanced. In this work, a PVDF/PET hydrophobic/hydrophilic membrane is prepared by non-solvent phase inducing method. Nanosized silica aerogel (SiAG) with high porosity is added to the composite membranes. The modifying effects and operating conditions on permeate flux and thermal efficiency in direct contact membrane distillation (DCMD) are investigated. Furthermore, the latent heat of vaporization and the heat transfer across the membranes are compared for SiAG addition, which indicates that the composite PVDF@SiAG/PET membranes display a great potential for distillation-separation application with high heat efficiency.
Postearthquake building damage assessment requires professional judgment; however, there are factors such as high workload and human error. Making use of Terrestrial Laser Scanning data, this paper presents a method for seismic damage information extraction. This new method is based
on principal component analysis calculating the local surface curvature of each point in the point cloud. Then use the nearest point angle algorithm, combined with the data features of the actual measured value to identify point cloud seismic information, and filter the points that tend to
the plane by setting the threshold value. Based on the statistical analysis of the normal vector, the raw point cloud data are deplanarized to obtain the preliminary results of seismic damage information. The density clustering algorithm is used to denoise the initially extracted seismic damage
information. Ultimately, we can obtain the distribution patterns and characteristics of cracks in the walls of the building. The extraction result of the seismic damage information point cloud data is compared with the photos collected at the site, showing that the algorithm steps successfully
identify the crack and shed wall skin information recorded in the site photos (identification rate: 95%). Point cloud distribution maps of cracked and shed siding areas determine quantitative information on seismic damage, providing a higher level of performance and detail than direct contact
measurements.
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