Small scale hot upwelling near the North Yellow Sea of eastern China

Abstract

[1] In order to image the structure of the upper-mantle discontinuity beneath Eastern China, we have applied a common conversion point (CCP) stacking method of receiver function (RF). Both the 410-km and the 660-km discontinuities (hereafter called the 410 and the 660) clearly show continuous positive phases along the selected profile. The 410 shows depression, whereas the 660 shows uplift, in the eastern section of the study profile. The transition zone (TZ) to the west of longitude 122°is thicker than the global average, though the TZ is thinner to the east of that longitude. The thinnest part of the TZ, with 10$15 km of thinning (an increase in temperature of up to 100°C), is located at the North Yellow Sea. We suggest that either the small-scale convection associated with the deep penetration of the sinking slab into the lower mantle, or a small plume from lower mantle, has generated hot upwelling in this region.

Crust-mantle coupling in North China: Preliminary analysis from seismic anisotropy

“…This pattern suggests that crustmantle coupling in North China cannot be explained by the simple decoupling SAF model or the strong coupling SAF model. Because of the inhomogeneous crust-mantle structure 47 17 in North China [3][4][5][6][7], the crust-mantle coupling relationship in this area possibly follows an inhomogeneous distribution of the two models or a model that gradually changes in terms of its physical properties. Considering the ~15° difference in the average polarization of fast shear-waves between the upper crust and the lithosphere, the substantive deformation in the upper crust and regions below the upper crust occurred at different points in geological history also support the likely requirement of model combination.…”

“…Velocity anomalies are predominantly distributed along NE-SW or NNE-SSW orientations, with E-W oriented belt-shaped and N-S oriented block-shaped characteristics. Uplift of the upper mantle was also locally found within this area [4][5][6][7].…”

Crust and upper mantle structure beneath Bohai Sea inferred from receiver function study

“…In this study, we chose 1D IASP91 velocity model with crustal structure modification based on H-κ stacking for each station in the CCP stacking. As an example, Figure 6 shows the depth variation for the stacking line at latitude 39.5 • N. The stacking profile is in the south part of the study region, the depths of the 410 change gradually from 410 km to 420 km between longitude 120.0 • E and 122.8 • E, and from 413 km to about 425 km between longitude 122.9 • E and 126.0 • E. On the other hand, the depths of the 660 change gradually from 674 km to 657 km between longitude 120.5 • E and 126.0 • E (Ai et al, 2008). Compared with the IASP91 model (Kennett and Engdahl, 1991), the 410 turns to be deeper whereas the 660 turns to be shallower near North Huanghai Sea.…”

“…The 410 and 660 (maximum amplitude part of converted phase) can be traced as continuous positive phases clearly in the study region. For the more details about bin sizes, velocity models and the 410 and 660 structures, we have already given the descriptions in Ai et al (2008). In this study, we chose 1D IASP91 velocity model with crustal structure modification based on H-κ stacking for each station in the CCP stacking.…”

“…BSN, operated from May 2005 to May 2006 by the author's group from the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS), consists of 20 portable broadband stations with Guralp CMG-3ESP sensors and Reftek 72-A digitizers. We selected teleseismic events from all above stations in the distance range between 30 • and 90 • with magnitude greater than 5.8 for the RF analysis (Ai et al, 2008).…”