Large restraining bends along active strike‐slip faults locally enhance the accumulation of clamping tectonic normal stresses that may limit the size of major earthquakes. In such settings, uncertain fault geometry at depth limits understanding of how effectively a bend arrests earthquake ruptures. Here we demonstrate fault imaging within a major restraining bend along the Altyn Tagh Fault of western China using the magnetotelluric (MT) method. The new MT data were collected along two profiles across the Aksay restraining double bend, which is bounded by two subparallel strands of the Altyn Tagh Fault: Northern (NATF) and Southern (SATF). Both two‐dimensional (2‐D) and three‐dimensional (3‐D) inversion models show that the Aksay bend may be the center of a positive flower structure, imaged as a high‐resistivity body extending to an ~40 km depth and bounded by subvertical resistivity discontinuities corresponding to the NATF and SATF. In the western section of the Aksay bend, both the NATF and SATF show similar low‐resistivity structure, whereas in the eastern part of the bend, the low‐resistivity anomaly below the SATF is wider and more prominent than that below the NATF. This observation indicates that the SATF shear zone may be wider and host more fluid than the NATF, lending structural support to the contention that fault slip at depth is asymmetrically focused on the SATF, even though surface slip is focused on the NATF. A south dipping, low‐resistivity interface branching upward from the SATF toward the NATF indicates a fault link between these strands at depth.
Soil screening could be a process of identifying and defining areas, contaminants, and condition at the sites that warrant further attention for developing ecological risk assessments. In present work, a total of 41 surface soil samples from Tianjin, China were sampled and the soil organic extracts were evaluated using a battery of in vitro cell bioassays. The battery included ethoxyresorfin O-deethylase (EROD) with H4IIE rat hepatoma cells bioassay for Aryl hydrocarbon (Ah) receptor (Ah-agonists) effects, the SOS/umu bioassay for genotoxic effects, and human estrogen receptor recombinant yeast bioassay for estrogenic effects. The results have showed that total estrogenic effects in these soil samples was measured to be between 0.1 and 14.2 ng EEQ kg À1 soil (d.w.); Ah-agonists effects assayed by EROD bioassay varied from 2.8 ng TEQ kg À1 soil (d.w.) to 42.6 ng TEQ kg À1 soil (d.w.), and the amounts of soil weight required for the extracts to lead positive result (IR 2.0) in the SOS/umu bioassay were between 3.9 and 31.3 mg (d.w.) per well. In addition, the geographic distributions of Ah-agonists effects and genotoxic effects in Tianjin area exhibited a strong positive correlation with each other. However, the distribution of estrogenic effects with high levels in northwest Tianjin was markedly different from that of Ah-agonists effects, where the high levels were distributed in the urban of Tianjin, as well as coastal towns. It has been concluded that the toxicity assessment of surface soil using a battery of in vitro cell bioassays could provided meaningful information regarding characterization procedure in ecological risk assessment.
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