Shaozhuo Liu

The Tibetan Plateau and surroundings host the largest number of modern glaciers outside the polar regions. However, the impact of (de)glaciation on present‐day geodetic measurements remains unclear. Using load deformation models, we examine the glacial isostatic uplift in response to (de)glaciation during the last glacial period and since the Little Ice Age. We find that the current glacial isostatic uplift locally exceeds 2.0 mm/yr near some glaciers in the Himalayas, Nyainqentanglha, Pamir, and Tien Shan. In the Nyainqentanglha, this glacial isostatic uplift could otherwise be misinterpreted as tectonic uplift associated with fictitious structures near the Jiali fault, a strike‐slip fault slipping at 2–5 mm/yr. In the Himalayas, the glacial isostatic uplift may contribute to 10%–40% of the observed 5–6 mm/yr geodetic uplift. In the Tien Shan, this ratio is 0%–50%. Therefore, glacial isostatic uplift must be considered when interpreting geodetic measurements in the Tibetan Plateau and surroundings.

The Southern Alps experiences rapid bedrock uplift and intense surface processes like erosion and deglaciation. We quantify how the erosion and deglaciation contribute to the ongoing vertical motions using geophysical models. The erosional unloading uplift is found to be 0.5–1.5 mm/yr throughout the central Southern Alps, whereas the recent deglaciation may locally produce uplift up to 1–3 mm/yr. The estimated unloading uplift accounts for 10%–40% of the GNSS‐observed uplift. After correcting the unloading uplift, the GNSS‐observed uplift can be explained by about 4–6 mm/yr dip‐slip motion on the Alpine fault, which is 10%–50% below previous geodetic estimates. Hence, unloading uplift must be evaluated when interpreting geodetic observations in tectonically active mountain ranges subjected to intense surface processes.

Reported fault slip rates, a key quantity for earthquake hazard and risk analyses, have been inconsistent for the northern Dead Sea fault (DSF). Studies of offset geological and archeological structures suggest a slip rate of 4 to 6 millimeters per year, consistent with the southern DSF, whereas geodetic slip-rate estimates are only 2 to 3 millimeters per year. To resolve this inconsistency and overcome limited access to the northern DSF in Syria, we here use burst-overlap interferometric time-series analysis of satellite radar images to provide an independent slip-rate estimate of ~2.8 millimeters per year. We also show that the high geologic slip rate could, by chance, be inflated by earthquake clustering and suggest that the slip-rate decrease from the southern to northern DSF can be explained by splay faults and diffuse offshore deformation. These results suggest a microplate west of the northern DSF and a lower earthquake hazard for that part of the fault.

High‐resolution present‐day earth surface deformation maps from satellites provide important data constraints, which help us better understand tectonic processes and analyze seismic hazards. Here, we use Sentinel‐1 Radar images (2014–2020) and accurate positioning measurements (2009–2019) to get a high‐resolution three‐dimensional earth surface velocity map for the northeastern Tibetan Plateau, and we invert the slip rate and coupling ratio of major regional faults. We find ∼4 mm/yr uplift along an arc from the Qilianshan to Lajishan, relative to the neighboring low‐elevation area to the east, which indicates ongoing rapid orogeny. We find transient deformation along the Laohushan and 1920 M8.5 Haiyuan rupture segments of the Haiyuan fault, whereas the western Haiyuan, southern Liupanshan, central Lajishan and central‐western West Qinling faults are essentially locked above 15–20 km, suggesting a potentially high seismic hazard.

Surprisingly fast bedrock uplift of ~5 mm/yr is observed by both GNSS and InSAR measurements across the central Southern Alps where oblique convergence is accommodated by the Alpine fault and other tectonic structures. This mountain range also features anomalously heavy precipitation and high erosion on the western side of the main divide. Since vertical motion is sensitive to perturbations from surface processes, we first evaluate how surface processes operating at different time scales (e.g., erosion, (de)glaciation, and hydrological loading) impact the present-day GNSS measurements. Erosion-induced rebound might be significant, but with an upper limit below 2 mm/yr uplift across the central Southern Alps, whereas elastic rebound caused by modern glacier melting and hydrological loading are secondary, as the magnitude is below 0.3 mm/yr at the locations of GNSS stations. Next, we use elastic dislocation models to explore the geometry and kinematics of a ramp-décollement system consistent with the GNSS-derived shortening and remaining vertical motions. Our best-fit model has 5.5-6.5 mm/yr reverse slip on the 40-50°SE-dipping Alpine fault locked above ~9 km depth, connected to a flat décollement accommodating 7.5-11.0 mm/yr of shortening. The remaining far-field shortening might be taken up by folding near the ramp-décollement junction and/or reverse slip along a NW-dipping backthrust in the hinterland. Our results present how climate-related surface and endogenic tectonic processes modulate the present-day vertical deformation across the central Southern Alps, giving new insights into active mountain building for this mountain range.

Part of the 5-km high Tibetan plateau is undergoing eastward extension and crustal thinning, which might be the signature of a waning orogeny. However, the actual extent of such processes throughout the high plateau remains uncertain. Here, we examine the impact of tectonic, geodynamic, and climate-related surface processes on the vertical deformation monitored since 2007 by continuous Global Positioning System (GPS) across the East Kunlun Shan (EKS), the largest relief inside the Tibetan plateau. GPS measurements reveal 1-2 mm/yr uplift of the EKS relative to the 2-km-lower Qaidam Basin. However, the range-perpendicular shortening is limited at most to ~1 mm/yr, which is not adequate to drive the observed vertical motion. Instead, (1) the isostatic response to erosion and regional deglaciation since the last glacial period likely accounts for a significant fraction, up to 40%, of our GPS derived vertical rate, and (2) the EKS and its surrounding region to the south are probably still rising at ~1 mm/yr, rather than subsiding. Thus, our results show that this part of the northern Tibetan plateau is rising, demonstrating that the Tibetan Plateau is still actively growing, in contrast with previous models proposing the passive demise of the high plateau due to erosion and gravitational collapse.

The present‐day motions in and around the Arabian plate involve a broad spectrum of tectonic processes including plate subduction, continental collision, seafloor spreading, intraplate magmatism, and continental transform faulting. Therefore, good constraints on the relative plate rates and directions, and on possible intraplate deformation, are crucial to assess the seismic hazard at the boundaries of the Arabian plate and areas within it. Here we combine GNSS‐derived velocities from 168 stations located on the Arabian plate with a regional kinematic block model to provide updated estimates of the present‐day motion and internal deformation of the plate. A single Euler pole at 50.93 ± 0.15°N, 353.91 ± 0.25°E with a rotation rate of 0.524 ± 0.001°/Ma explains well almost all the GNSS station velocities relative to the ITRF14 reference frame, confirming the large‐scale rigidity of the plate. Internal strain rates at the plate‐wide scale (∼0.4 nanostrain/yr) fall within the limits for stable plate interiors, indicating that differential motions are compensated for internally, which further supports the coherent rigid motion of the Arabian plate at present. At a smaller scale, however, we identified several areas within the plate that accommodate strain rates of up to ∼8 nanostrain/yr. Anthropogenic activity and possible subsurface magmatic activity near the western margin of the Arabian plate are likely responsible for the observed local internal deformation. Put together, our results show a remarkable level of stability for the Arabian lithosphere, which can withstand the long‐term load forces associated with active continental collision in the northeast and breakup to the southwest with minimal internal deformation.

The Yinchuan‐Jilantai rift system (YJRS) is a prominent Cenozoic intracontinental rift zone located along the northwestern margin of the Ordos Block in western North China. Although the absence of volcanism indicates a passive origin, the tectonic driving forces and rift‐related deep processes remain poorly understood. Here we use newly obtained broadband magnetotelluric (MT) data to image the lithospheric electrical structure along a ∼500‐km‐long profile across the YJRS. At middle–lower crustal levels, the resulting model reveals several subvertical, crustal‐scale conductors that spatially correlate with the rift‐parallel, high‐angle normal faults. We attribute these features to a combined effect of saline fluids and partial melt due to recent supply of heat and volatiles into the crust from below. The crustal‐penetrating normal faults that were reactivated during extension serve as permeable pathways for deep fluid migration. In the uppermost mantle, a ∼400‐km‐wide zone of enhanced conductivity is present and requires the presence of partial melt. We interpret this feature as evidence for lithospheric modification through upwelling and decompressional melting of the volatile‐enriched mantle. When compared with the narrow (<100‐km‐wide) mantle conductors imaged beneath the Shanxi rift system along the eastern margin of the Ordos Block, such a feature indicates the YJRS has experienced a larger extent of lithospheric modification. Combined with additional geologic and geophysical observations, we attribute this essential difference to the inherited lithospheric heterogeneity and the eastward decreasing far‐field impacts from the India‐Eurasia collision.