The amplification effect of PGA and the large-scale liquefaction-triggered mudflow during the December 18,2023 M 6.2 Jishishan Earthquake in Gansu Province,China

At 23:59 on December 18, 2023, a strong earthquake (M 6.2) struck Jishishan County in Gansu province, China, which is situated in the transition zone between Qinghai-Xizang Plateau and the Loess Plateau.The focal depth is 10 km, and the epicenter (35.70°N and 102.79°E) is about 100 km southwest away from Lanzhou, the capital city of Gansu province. As of December 31, 2023, the earthquake has caused 151 people dead and 979 people wounded in Gansu and Qinghai.

The response law of far-field seismic ground motion of the Wenchuan earthquake and its damaging mechanism in the Loess Plateau

A series of housing collapses and other serious damage was caused by the 2008 Wenchuan M_(S)8.0 earthquake in the seismic intensity Ⅵ areas of the Loess Plateau, which is hundreds of kilometers away from the epicenter, and which showed a remarkable seismic intensity anomaly. The seismic disasters are closely related to the seismic response characteristics of the site, therefore, the systematic study of the far-field seismic response law of the Wenchuan earthquake in the Loess Plateau is of great significance to prevent the far-field disaster of great earthquake. In this paper, the seismic acceleration records of several bedrock stations and loess stations from the seismogenic fault of the Wenchuan earthquake to the Loess Plateau were collected, and the attenuation law of ground motion along the propagation path and the characteristics of seismic response on the loess site are studied,and the mechanism of amplification effect of ground motion is analyzed based on the dynamic feature parameters of the loess site obtained through the HVSR method. Taking a typical loess site of thick deposit as the prototype, a series of shaking table tests of dynamic response of loess site models with different thicknesses were carried out.Amplification effect, spectral characteristics of acceleration in model sites were analyzed under the action of a farfield seismic wave of the Wenchuan earthquake. The results show that seismic attenuation on the propagation path along the NE strike of the seismogenic fault to the Loess Plateau is slower than that in other directions, and the predominant period range of ground motion on bedrock site of the Loess Plateau presents broadband characteristics. Because the natural periods of loess sites with thick deposits are within the predominant period range of bedrock input wave, loess sites appear significant amplification effect of ground motion, the horizontal acceleration of ground motion exceeds 0.1 g, the seismic intensity reaches 7°. The thicker the loess deposit is, the more significant the change of spectral characteristics of ground motion on loess sites, and the narrower the predominant period range of ground motion becomes, and the closer it is to the natural period of loess sites.Therefore, for some old houses on thick loess sites, the poor seismic performance and strong seismic response eventually led to their collapses and damages because their natural periods are very close to the predominant period of ground motion of the Wenchuan earthquake on thick loess sites;For these damaged high-rise buildings,the resonance effect might be the main reason for their damages because their natural periods are included in the predominant period range of ground motion of the Wenchuan earthquake on thick loess sites.These research results would provide a basis for seismic disasters prediction and evaluation and seismic design of construction engineering in the Loess Plateau.

Relationship between circadian rhythm and brain cognitive functions

Circadian rhythms are considered a masterstroke of natural selection,which gradually increase the adaptability of species to the Earth’s rotation.Importantly,the nervous system plays a key role in allowing organisms to maintain circadian rhythmicity.Circadian rhythms affect multiple aspects of cognitive functions(mainly via arousal),particularly those needed for effort-intensive cognitive tasks,which require considerable top-down executive control.These include inhibitory control,working memory,task switching,and psychomotor vigilance.This mini review highlights the recent advances in cognitive functioning in the optical and multimodal neuroimaging fields;it discusses the processing of brain cognitive functions during the circadian rhythm phase and the effects of the circadian rhythm on the cognitive component of the brain and the brain circuit supporting cognition.