RESUMO
In order to ascertain the impact of the Tohoku-Oki 3.11 M9.0 earthquake on the stability of the faults in the Beijing Plain, we investigated the adjustment of the in situ stress field of the Beijing Plain after this earthquake based on in situ stress monitoring data. Then, we analyzed the stability of the five main faults in each adjustment stage of the in situ stress field based on the Mohr−Coulomb failure criteria and Byerlee's law. Finally, we studied the fault slip potential (FSP) of the main faults under the current in situ stress field. The research results show that (1) after the Tohoku-Oki 3.11 M9.0 earthquake, the tectonic environment of the Beijing Plain area changed rapidly from nearly EW extrusion to nearly EW extension, and this state was maintained until June 2012. After this, it began to gradually adjust to the state present before the earthquake. As of September 2019, the tectonic environment has not recovered to the state present before the earthquake. (2) The ratios of shear stress to normal stress on the fault plane of the fault subsections in the three time periods before the Tohoku-Oki 3.11 M9.0 earthquake, 6 June 2012 and 8 September 2019 were 0.1−0.34, 0.28−0.52, and 0.06−0.29, respectively. It shows that the stress accumulation level of faults in the Beijing Plain area increased in a short time after the earthquake and then gradually decreased. (3) Under the current in situ stress field, most of the subsections of the five main faults have a low FSP (<5%). The areas with high FSP are mainly concentrated in the central and southeastern parts of the Beijing Plain, including the Nankou-Sunhe fault, the northern section of the Xiadian fault, and the areas where the five faults intersect.
RESUMO
Glomalin-related soil protein (GRSP) is a hydrophobic protein released by arbuscular mycorrhizal fungi. It is an important component of the soil carbon pool, and it improves the soil aggregate structure; however, it remains unclear whether GRSP can enhance soil carbon sequestration and improve soil quality during rapid urbanization. The built-up area in Nanchang, China was the study area, and the proportion of impervious surface area was the parameter of urbanization intensity. A total of 184 plots (400 m2) were set up to collect soil samples (0-20 cm) for analysis. Aggregates of five particle sizes were sieved, and the percentage amounts of soil organic carbon (SOC) and GRSP for them were determined. The results showed that the easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP) contents of the four aggregates of <2 mm were 22-46% higher in low urbanization areas than those in high urbanization areas (p < 0.05), indicating that the higher urbanization intensity was associated with the lower GRSP content of different aggregates. The GRSP was significantly positively correlated with SOC (p < 0.05). Moreover, the contribution of GRSP to the SOC pool in the <0.25 mm aggregate was significantly higher than that in other aggregates. In addition, the EE-GRSP content was significantly positively correlated with mean weight diameter (MWD) and geometric mean diameter (GMD) in the four aggregates of <2 mm, whereas it was negatively correlated with fractal dimension (D) in the >2 mm, 1-2 mm and <0.053 mm aggregates. The T-GRSP content showed significant correlations only with MWD, GMD, and D in the 1-2 mm aggregate. This study revealed that increasing urbanization intensity can significantly reduce the GRSP content of different sized aggregates. Moreover, the GRSP content significantly promoted SOC sequestration, and the EE-GRSP content more significantly promoted soil aggregate stability than that of the T-GRSP. These findings provide new ideas for exploring the improvement of soil quality during the process of urbanization.