The Gobi Altai region of southern Mongolia has been in the Eurasian plate interior since the midMesozoic,yet has experienced episodic phases of deformation since that time.In this paper,we document field evidence to c...The Gobi Altai region of southern Mongolia has been in the Eurasian plate interior since the midMesozoic,yet has experienced episodic phases of deformation since that time.In this paper,we document field evidence to characterize and date the intra-plate tectonic history of the Gobi Altai region from the Triassic to the present.To this end,we provide detailed mapping of the structure and stratigraphy of the eastern flanks of Mt.Ih Bogd that contains the widest variety of rock-time units in the area.We carry out geochronological analysis of basaltic lavas and basement granite in the area.We demonstrate that a crystalline basement with a 502 ± 8 Ma granitoid（U/Pb） underwent two phases of basin formation in the Mesozoic.which we date with new40Ar/39Ar lava ages of 218.5 ± 1.5,123.2 ± 0.7 and 124.8 ± 1.2 Ma,respectively.Both phases are linked to deposition of fluvio-lacustrine sediments and trap-like basaltic volcanics,with cumulative thicknesses of 1000-1500 m.Both basins were likely north-facing half-grabens that developed underN-S extension,but were subsequently overthrusted by Paleozoic and older crystalline basement during a less well constrained,but likely mid-Cretaceous phase of N-S shortening and basin inversion.Our results are consistent with recent seismic imaging of rift basins100 km to the NE of the study area where a similar history was reconstructed.The multiple phases of intra-plate deformation appear to have parallel structural trends,most likely due to reactivated Paleozoic basement structures created during the original terrane amalgamation of the Central Asian Orogenic Belt continental crust.This strong basement heterogeneity may predispose it to reactivation,and make it sensitive to changes in the overall stress field of the Eurasian plate driven by forces at its margins and base.Detailed study of Mongolia’s multi-stage tectonic history may thus provide a key proxy for the long-term dynamics of the Eurasian plate.In addition,the repeated reactivation of the Gobi Altai region during the last 200 My supports the contention that non-cratonized continental interior regions composed of Phanerozoic terrane collages are particularly susceptible to fault reactivation,much more than older cratonized continental crust.展开更多
Predicting approximate earthquake-induced landslide displacements is helpful for assessing earthquake hazards and designing slopes to withstand future earth- quake shaking. In this work, the basic methodology outlined...Predicting approximate earthquake-induced landslide displacements is helpful for assessing earthquake hazards and designing slopes to withstand future earth- quake shaking. In this work, the basic methodology outlined by Jibson （1993） is applied to derive the Newmark displacement of landslides based on strong ground-motion recordings during the 2013 Lushan Ms 7.0 earthquake. By analyzing the relationships between Arias intensity, New- mark displacement, and critical acceleration of the Lushan earthquake, formulas of the Jibson93 and its modified models are shown to be applicable to the Lushan earthquake dataset. Different empirical equations with new fitting coefficients for estimating Newmark displace- ment are then developed for comparative analysis. The results indicate that a modified model has a better goodness of fit and a smaller estimation error for the Jibson93 formula. It indicates that the modified model may be more reasonable for the dataset of the Lushan earthquake. The analysis of results also suggests that a global equation is not ideally suited to directly estimate the Newmark displacements of landslides induced by one specific earthquake. Rather it is empirically better to perform a new multivariate regression analysis to derive new coefficients for the global equation using the dataset of the specific earthquake. The results presented in this paper can be applied to a future co-seismic landslide hazard assessment to inform reconstruction efforts in the area affected by the 2013 Lushan Ms 7.0 earthquake, and for future disaster prevention and mitigation.展开更多
基金UK NERC Grant NER/D/S/2003/00671 to WDCThe 2005 fieldwork of DJJvH was partly supported by an E.J.Garwood Grant of the Geological Society of London+1 种基金GBS was supported by the Molengraaff Foundation and the KF Hein FoundationDJJvH acknowledges funding through ERC Starting Grant 306810(SINK)and an NWO VIDI grant
文摘The Gobi Altai region of southern Mongolia has been in the Eurasian plate interior since the midMesozoic,yet has experienced episodic phases of deformation since that time.In this paper,we document field evidence to characterize and date the intra-plate tectonic history of the Gobi Altai region from the Triassic to the present.To this end,we provide detailed mapping of the structure and stratigraphy of the eastern flanks of Mt.Ih Bogd that contains the widest variety of rock-time units in the area.We carry out geochronological analysis of basaltic lavas and basement granite in the area.We demonstrate that a crystalline basement with a 502 ± 8 Ma granitoid（U/Pb） underwent two phases of basin formation in the Mesozoic.which we date with new40Ar/39Ar lava ages of 218.5 ± 1.5,123.2 ± 0.7 and 124.8 ± 1.2 Ma,respectively.Both phases are linked to deposition of fluvio-lacustrine sediments and trap-like basaltic volcanics,with cumulative thicknesses of 1000-1500 m.Both basins were likely north-facing half-grabens that developed underN-S extension,but were subsequently overthrusted by Paleozoic and older crystalline basement during a less well constrained,but likely mid-Cretaceous phase of N-S shortening and basin inversion.Our results are consistent with recent seismic imaging of rift basins100 km to the NE of the study area where a similar history was reconstructed.The multiple phases of intra-plate deformation appear to have parallel structural trends,most likely due to reactivated Paleozoic basement structures created during the original terrane amalgamation of the Central Asian Orogenic Belt continental crust.This strong basement heterogeneity may predispose it to reactivation,and make it sensitive to changes in the overall stress field of the Eurasian plate driven by forces at its margins and base.Detailed study of Mongolia’s multi-stage tectonic history may thus provide a key proxy for the long-term dynamics of the Eurasian plate.In addition,the repeated reactivation of the Gobi Altai region during the last 200 My supports the contention that non-cratonized continental interior regions composed of Phanerozoic terrane collages are particularly susceptible to fault reactivation,much more than older cratonized continental crust.
基金Acknowledgements The authors would like to express sincere appreciation to the reviewers for their valuable comments and suggestions, which were helpful for improving the MS. This work was financially supported by the Basic Science Fund of the Institute of Geology, China Earthquake Administration （IGCEA-1401）, and the National Natural Science Foundation of China Projects （Grant Nos. 41372219, 41272298, and 41172193）, for which grateful appreciation is expressed. We also would like to state our deep appreciation to the China Strong Motion Networks Center for supplying recordings of strong motion.
文摘Predicting approximate earthquake-induced landslide displacements is helpful for assessing earthquake hazards and designing slopes to withstand future earth- quake shaking. In this work, the basic methodology outlined by Jibson （1993） is applied to derive the Newmark displacement of landslides based on strong ground-motion recordings during the 2013 Lushan Ms 7.0 earthquake. By analyzing the relationships between Arias intensity, New- mark displacement, and critical acceleration of the Lushan earthquake, formulas of the Jibson93 and its modified models are shown to be applicable to the Lushan earthquake dataset. Different empirical equations with new fitting coefficients for estimating Newmark displace- ment are then developed for comparative analysis. The results indicate that a modified model has a better goodness of fit and a smaller estimation error for the Jibson93 formula. It indicates that the modified model may be more reasonable for the dataset of the Lushan earthquake. The analysis of results also suggests that a global equation is not ideally suited to directly estimate the Newmark displacements of landslides induced by one specific earthquake. Rather it is empirically better to perform a new multivariate regression analysis to derive new coefficients for the global equation using the dataset of the specific earthquake. The results presented in this paper can be applied to a future co-seismic landslide hazard assessment to inform reconstruction efforts in the area affected by the 2013 Lushan Ms 7.0 earthquake, and for future disaster prevention and mitigation.
