Search

Compelling evidence indicates that continental crust can subduct to >300 km and even enter the mantle transition zone (MTZ). However, detecting continental materials within the deep Earth is challenging due to our incomplete knowledge about their physical properties at mantle conditions. We use a newly compiled mineral‐physical database coupled with thermodynamic modeling to calculate seismic velocities of the subducted continental crust (SCC) beyond 150 km. Results show that the SCC has one seismically detectable window depth (300–390 km) with ∼4% VP anomaly. Besides, the upper crust has another two window depths (<250 km and 610–660 km) with anomalies of −6.4%–−1.6% and −7.6%–−2.2%, and 3.6%–7.9% and 3.9%–8.6% for VP and VS compared to those of the ambient mantle, respectively. These predicted SCC characteristics match seismic anomalies at mantle depths and suggest subducted upper crust potentially contributing to the high‐velocity anomalies in the MTZ. Plain Language Summary: In this study, we explore how pieces of Earth's outer layer, known as the continental crust, can dive deep into the layer beneath it, called the mantle, reaching depths of up to 660 km. Seismologists struggle to observe this because using current seismological methods is hard to detect crustal signals beyond 150–180 km. To address this challenge, we performed detailed calculations using a newly compiled mineral‐physical database to understand how subducted continental crust (SCC), behave under high pressures and temperatures. Our research reveals a specific depth range, from 300 to 390 km, where the SCC produces a unique seismic signal that stands out by about 4%. Additionally, the upper parts of the continental crust show distinct signals below 250 km and between 610 and 660 km due to variations in seismic velocities and their ratios. Our findings help to map out where these hidden pieces of crust can be found in the Earth's mantle, corroborating with seismic data from regions such as the Hindu Kush and Myanmar, as well as in the mantle transition zone beneath ancient continental areas. This work opens new pathways for understanding the Earth's inner dynamics and the fate of its crustal components over geological timescales. Key Points: We compiled a new mineral‐physical database for subducted lithosphere derived from experimental results and first‐principle calculationsThermodynamic modeling indicates a seismically detectable window depth for bulk continental crust and two additional depths for upper crustHigh VP anomalies in the mantle transition zone may represent subducted upper continental crust [ABSTRACT FROM AUTHOR]

High‐resolution seismic model is crucial for advancing our understandings on geological processes and enhancing seismic hazard mitigation programs. We construct a high‐resolution China Seismological Reference Model (CSRM‐1.0) in the top 100 km of the crust and uppermost mantle in continental China following a top‐down construction process. The employed seismic constraints include P‐wave polarization angle from tele‐seismic event, short‐period Rayleigh wave ellipticity from ambient noise, long‐period Rayleigh wave ellipticity from earthquake data, receiver function, empirical Green's function from ambient noise, Rayleigh wave phase/group velocity dispersion curves from regional earthquakes, and Pn‐wave travel time extracted from seismic data of 4,435 stations. CSRM‐1.0 has a spatial crustal resolution of ∼60 km beneath the north‐south seismic belt and trans‐North China orogen regions and ∼120 km beneath the rest of continental China, and a spatial mantle resolution of ∼300 km. CSRM‐1.0 exhibits prominent velocity heterogeneities in the crust and uppermost mantle and an eastward thinning of the crust, geographically correlating with geological settings. CSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM‐1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter‐block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter‐block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM‐1.0 to the CSRM product center (http://chinageorefmodel.org) as a backbone open‐access geophysical cyberinfrastructure. Plain Language Summary: High‐resolution seismic imaging of the crust and uppermost mantle offers crucial insights into regional geological histories and enhances seismic and volcanic hazard mitigation programs. We construct a high‐resolution China Seismological Reference Model (CSRM‐1.0) of the crust and mantle beneath continental China with various types of seismic constraints extracted from seismic data recorded by 4,435 stations deployed across continental China since 1990. CSRM‐1.0 has a spatial resolution of ∼60–120 km in the crust and 300 km in the uppermost mantle. CSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM‐1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter‐block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter‐block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM‐1.0 to the CSRM product center (http://chinageorefmodel.org) as a backbone open‐access geophysical cyberinfrastructure. Key Points: CSRM‐1.0 is constructed with various seismic constraints from data of 4,435 stations using a self‐consistent top‐down construction processCSRM‐1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution, and enhanced model accuracyCSRM‐1.0 reveals major crustal mafic rocks related to the past subductions, an Emeishan mantle plume and geological inter‐block boundaries [ABSTRACT FROM AUTHOR]

Soldier tactical training is the basic movement in combats. Traditional soldier tactical training and test is finished by artificial timing and judgment which has some problems, such as low detection accuracy, low data collection and storage efficiency. Meanwhile, there are no effective solutions for the problems. Based on FPGA/MCU platform, a kind of soldier tactical training and test system is designed and implemented. The system adopted a few pairs of active correlation infrared detector, for collecting touch signals and wireless data transmission utilizing hand-held terminal. The backstage provides guidance and suggestions by analyzing data. Test results proves that the system can solve problems in current soldier tactical trainings.

In order to explore the rational use of nursing resources in the epidemic situation of COVID-19, we optimized the shift arrangement in COVID-19 isolation area and constructed a reasonable nursing schedule under the condition of limited human resources. Seventy-eight nurses were arranged in COVID-19 isolation area to work for 1 week according to 3 different shifts: 4 + 4 h, 6 h and 6 h (overlapping by 1 h). Through the form of questionnaire, the comprehensive job satisfaction of 3 different models were compared, and the nursing quality and the consumption of protective equipment under 3 different modes were analyzed. The results showed that the comprehensive job satisfaction and nursing quality of nurses in 6 h (overlapping by 1 h) shift mode were better than those in other shift modes, and the consumption of protective equipment was lower.

Based on sol-gel method and spin coating process, TiO2 film doped with Li+ is prepared by utilizing analytical pure butyl titanate, lithium nitrate, absolute ethanol, glacial acetic acid, acetylacetone and deionized water as raw material. The Li+ ion which has equal radius as Ti4+ ion is chosen in experiments for doping and modification. Experimental results show certain increase of catalytic efficiency in TiO film doped with Li+. However, the increase level of catalytic efficiency gradually shows some decrease when the dopant amount changes from 0.025mol to 0.1mol. Catalytic efficiency is raised to 25.7% when the dopant amount is 0.025mol.