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Using the three component acceleration records of the National Strong Motion Observation Network System (NSMONS) and the National Seismic Intensity Rapid Reporting and Earthquake Early Warning Network, the ground motion attenuation characteristics, spatial distribution, source rupture direction, and near-fault pulse characteristics of the Luding MS6.8 earthquake were analyzed. Comparing the observed values of peak ground acceleration (PGA), peak ground velocity (PGV), pseudo-spectral acceleration (PSA), and 90% significant duration (SD) with several typical ground motion prediction equations (GMPE), it was found that the ground motion attenuation characteristics of this earthquake are consistent with GMPE for the southwest region, but overall lower than the global model average level. In the comparison of between-event residuals, this earthquake exhibits different characteristics from the same magnitude thrust type earthquake. The within-event residuals reflect that the anelastic attenuation in the Luding region is slightly weaker than that in the Menyuan region. In terms of spatial distribution of ground motion parameters, the PGV and PSA with a period of 1.0 to 8.0 s have significantly higher intensity in the southeast direction of the epicenter than in other directions. Based on PGV, it is speculated that the source rupture direction of the earthquake was 151°, which is close to the fault strike of 163°. Pulse-like ground motions were identified in up to 12 sets of near-fault records with pulse periods significantly lower than historical earthquakes of similar magnitudes. Stations with pulse peak values greater than 40 cm·s−1 in the pulse dominant direction of the velocity time history all appeared in the narrow band area ahead of the rupture direction. The distribution area of near-fault pulses is highly correlated with the distribution of high macroseismic intensity areas and landslide areas, and it is necessary to pay attention to the impact of near-fault pulses in seismic fortification. [ABSTRACT FROM AUTHOR]

Emergency centers, communication systems, and hospitals are essential infrastructures for emergency rescue and subsequent reconstruction activities. An investigation into the Nepal 2015 earthquake sequences found that the visited government offices were functioning normally 40 days after the main shock; that the local media failed to coordinate with the entire society at the beginning, but mobile phone-based communication recovered quickly; and that the hospitals in high-intensity areas were badly damaged as a result of improper design and adverse site configuration. Recommendations are proposed to enhance the aseismic capacity of structural and non-structural components using earthquake early warning and base isolation. [ABSTRACT FROM AUTHOR]

The Gorkha earthquake in Nepal led to many landslides and severe damage to the transportation infrastructure. After careful comparison of the aerial photographs and satellite images before and after the earthquake, partially verified by a field study, more than 2,064 landslides and many road failures were observed. Many bridges, especially steel-truss and suspension bridges, suffered little damage from inertia loads during the earthquake, but were severely damaged due to rockfalls. Potential geological hazards hindered the delivery of supplies in mountainous areas, and road closures impeded the overall speed of rehabilitation. [ABSTRACT FROM AUTHOR]

The 7.8 Mw Gorkha earthquake struck the east of Lamjung in Nepal, followed by a sequence of powerful aftershocks. Chinese Team Six including the authors inspected the seismic damage to civil structures along 10 paths in densely populated areas with a seismic intensity of VII to IX, 40 days after the main shock. The damage was categorized according to structure types and described in detail. Several conclusions are made: powerful aftershocks can significantly affect the failure patterns; geological conditions, structure types, and height have great influence on the level of damage; and the local risky retrofitting technique needs improvement badly. [ABSTRACT FROM AUTHOR]

On 3 August 2014, the Ludian earthquake struck northwest Yunnan Province with a surface wave magnitude of 6.5. This moderate earthquake unexpectedly caused high fatalities and great economic loss. Four strong motion stations were located in the areas with intensity V, VI, VII and IX, near the epicentre. The characteristics of the ground motion are discussed herein, including 1) ground motion was strong at a period of less than 1.4 s, which covered the natural vibration period of a large number of structures; and 2) the release energy was concentrated geographically. Based on materials collected during emergency building inspections, the damage patterns of adobe, masonry, timber frame and reinforced concrete (RC) frame structures in areas with different intensities are summarised. Earthquake damage matrices of local buildings are also given for fragility evaluation and earthquake damage prediction. It is found that the collapse ratios of RC frame and confined masonry structures based on the new design code are significantly lower than non-seismic buildings. However, the RC frame structures still failed to achieve the 'strong column, weak beam' design target. Traditional timber frame structures with a light infill wall showed good aseismic performance. [ABSTRACT FROM AUTHOR]

The clipping of near-field seismic waveforms caused by instrument limitations results in the waste of lots of waveforms and hinders the effective advancement of seismic research projects like source parameter inversion, near-fault ground motion characteristics, and earthquake early warning (EEW). In this paper, we propose to use the cubic spline interpolation method to restore the clipping waveform to solve the near-field data loss. We evaluate the recoverability of seismic waveforms with different clipped levels through artificial clipping experiments and compare the recovery waveforms with the projection onto convex sets (POCS) method. The results show that the restoration deviation of the cubic spline interpolation method is less than 1% at the clipped point, for the records whose clipped amplitude does not exceed 50% of the peak. In addition, the restored phase feature of the cubic spline interpolation is closer to the real waveform than the POCS method. To verify the performance of this method in the realistic earthquake, we apply it to the Barkam Mw 5.9 earthquake. The results show that the peak ratio of the restored clipping records to the measured non-clipping records is close to 1, and the relative error of the response spectrum is less than 0.1. Finally, we apply this method to successfully restore about 60% of near-field clipped records from the 2022 Lushan Mw 5.8 earthquake, which provided more data support for the study of the near-field ground motion. [ABSTRACT FROM AUTHOR]

Ground motion amplification induced by topography plays a vital role in engineering seismology. A topographic array of 8 accelerographs has been operating along the ridge in Xishan Park since 2007. The topographic site effects in Zigong city are studied based on the strong motion data of 2008 Ms 8.0 Wenchuan earthquake (the epicentral distance = 225 km) and 2019 Ms 5.2 Zizhong earthquake (the epicentral distance = 29 km). We compare the peak ground acceleration (PGA) of the two earthquakes and find that the PGA of Station 7#, which locates on a relatively steep slope, is amplified by 4.41 times comparing with the reference station in Zizhong earthquake, while this value is only 1.62 in Wenchuan earthquake. Fourier amplitude spectrum shows that the high frequency content of Zizhong earthquake is more abundant because of its smaller epicentral distance. By using the standard spectral ratio (SSR) method, we conclude that the amplification occurs because high-frequency ground motion is likely to resonate at small-scale features. Finally, the 3D numerical simulations are used to verify these conclusions. Our work indicates that more sophisticated numerical models need to be established for more accurate topographic site effects quantification. In addition, the influence of nearby topographic features should be considered when selecting reference stations. Highlights: PGA value tends to increase with elevation of the ridge and reaches maximum at the crest or its vicinity. Ground motion is amplified at the slope crest and de-amplified at the bottom. 3D numerical simulation indicates that high-frequency ground motions are likely to resonate on small-scale features. [ABSTRACT FROM AUTHOR]