Post-Mesozoic Transformation of Tectonic Domain in Southeastern China and Its Geodynamic Mechanism

Since the Mesozoic and Cenozoic, a transformation from a Tethyan Himalayan tectonic domain into a circum Pacific tectonic domain from Indosinian to Yanshanian is indicated in this paper, resulting in conspicuous changes in geophysics, tectono magmatic distribution, lithofacies and paleo geography, tectonic system in southeastern China. Tectonic analysis shows that the tectonic framework resulted from the compounding, transforming and superimposing of the two tectonic domains. The geodynamic mechanism of the transformation is mainly shown as the transverse and longitudinal heterogeneity of lithosphere, and the exchange between the crust and the mantle.

On the Geodynamic Mechanism of Episodic Uplift of the Tibetan Plateau during the Cenozoic Era

Multi-stage uplift of the Tibetan Plateau during the Cenozoic implies a complex geodynamic process.In this paper,we review main geodynamic models for the uplift of the plateau,and,in particular,analyze the spatio-temporal framework of the Cenozoic deformation structures,which are closely related to the deep geodynamic mechanism for the plateau uplift.From this perspective,significant change of the deformation regime over the Tibetan Plateau occurred by the middle-late Miocene,while thrust and thrust-folding system under NS compression was succeded by extension or stress-relaxation.Meanwhile,a series of large-scale strike-slip faults commenced or was kinemtically reversed.Based on a systematic synthesis of the structure deformation,magmatism,geomorphological process and geophysical exploration,we propose a periodical model of alternating crustal compression and extension for episodic uplift of the Tibetan Plateau.

The Geodynamic Mechanism of the M_S8.0 Wenchuan Earthquake

Located on the east boundary of Qinghai-Xizang （Tibet） Plateau, the Ms8.0 Wenchnan earthquake is the strongest event to hit the active block since the 2001 Kunlun Mountains Pass earthquake. In this study, a simplified source model of the Wenchnan earthquake is constructed based on the deep/shallow tectonic settings and crust/mantle structure features of the Longmenshan thrust fault zone. On the basis of dynamic model abstraction, we construct a system of dynamical equations for the seismogenic process and obtain the analytical expressions of stress and strain in the seismogenic process. A preliminary study of the seismogenic process of the Ms8.0 Wenchuan earthquake, based on the analytical solution of the model and observation of tectonic deformation in the Longmenshan region, indicates that the seismogenic process of the Wenchuan earthquake took place over a period of more than 3200 years. The slow process of seismogeny and the long recurrence period of strong earthquakes are attributed to the low deformation rate of the Longmenshan tectonic zone.

Numerical investigation on the geodynamical mechanism of the first major shock of 2006 Pingtung M_w7.0 earthquake

A strong Mw7.0 earthquake struck Pingtung offshore of Talwan on December 26, 2006. It consisted of two major events with an 8-minute interval. The first major shock occurred at 12：26 UTC. Focal mechanism results from Harvard, USGS, and BATS all indicated that the first major shock was a normal fault earthquake and the second one was dominated by strike-slip offsets. The location of the epicenter varied greatly in depth in different analyses. The latest results showed that the focal depth of the first shock was most probably around 40-44 km, placing the epicenter in the lithospheric mantle. However, this is not a location where earthquakes usually occur. To explore the geodynamical mechanism of this event, we carded out 2D finite element method （FEM） numerical experiments. Our primary results indicate that the geodynamical background, as well as the formation of Pingtung earthquake, is a consequence of the collision between Luzon arc and Chinese continental margin. Although Taiwan Island is in the shadow of NW-SE trending compressive collision zone, the existence of ductile lower crust leads to the decoupling between upper crust and lithospheric mantle. As lithospheric mantle subducts to the depth of around 250 km, the upper part of the bending subduction slab puts itself in an extensional state. The extensional stress from bending induced the occurrence of this normal fault earthquake at the critical point.

Fault Systems and Their Mechanisms of the Formation and Distribution of the Tarim Basin,NW China

This article aims to analyze the main controlling factors of development, distribution and evolution of the fault systems in the Tarim Basin. Based on the seismic profile interpretation, compre- hensive analysis of the drilling and geologic data, six fault systems maybe recognized in the Tarim Basin, they are the foreland fault system of the South Tianshan Mountain, the northern Tarim uplift fault sys- tem, North Tarim depression fault system, central fault system, Southwest Tarim fault system, and Southeast Tarim fault system. It is indicated that the main differences exist at the development, evolu- tion and distribution of the fault systems in the Tarim Basin. The sub-fault systems can be recognized according to the differences of the fault development and distribution in the interior of the fault system. It is characterized that the multi-level differential development and distribution of the fault systems ex- ist in the Tarim Basin. The fault belt developed in the Paleozoic strata mainly distribute at the pa- leo-uplift and paleo-slope in the interior of the Tarim Basin, and the fault belt occurred in the Meso-Cenozoic beds mainly develop at the peripheral foreland depressions. Zonal and segment differ- ential development and distribution of the fault systems also exist in the Tarim Basin. The formation and distribution of the Tarim fault systems is of complex controlling mechanisms. Poly-phase structural movement and tectonic transition controls the multi-phase differential development and distribution of the fault systems in the Tarim Basin. Multi-level differential development and distribution is controlled by multi-level detachment belt and regional unconformities. Zonal and segment differential develop- ment and distribution of the Tarim fault systems maybe controlled by pre-existed basement structural texture. The major direction of the fault systems in the Tarim Basin is controlled by the later stage basin-mountain coupling.