Description: The MW7.1 Anchorage earthquake is the most destructive earthquake since the 1964 MW9.2 great Alaska earthquake in the United States. In this study, high-rate GPS data and near-field broadband seismograms are used in separate and joint inversions by the generalized Cut-and-Paste (gCAP) method to estimate the focal mechanism. In order to investigate the influence of crustal velocity structure on the focal mechanism inversion results, two velocity models (Crust1.0 and Alaska Earthquake Center (AEC)) are used for detailed comparison and analysis. The results show that: (1) The two nodal planes of the optimal double-couple solution are nearly north-south striking, with dip angles of about 30° and 60°respectively, and the centroid focal depth is 54–55 km, which is an intraplate normal fault event. (2) The inversion results for the two types of data and the two velocity models are consistent with some previous studies, which indicates that the results are stable and reliable. The more accurate velocity structure model is helpful for focal mechanism inversion of the complex earthquake. (3) The inclusion of high-rate GPS data in joint inversion provides a more effective constraint on centroid depth. © 2021 The Authors

Description: In this study, Sentinel-1 and Advanced Land Observation Satellite-2 (ALOS-2) interferometric synthetic aperture radar (InSAR) and global positioning system (GPS) data were used to jointly determine the source parameters and fault slip distribution of the Mw 6.6 Hokkaido eastern Iburi, Japan, earthquake that occurred on 5 September 2018. The coseismic deformation map obtained from the ascending and descending Sentinel-1 and ALOS-2 InSAR data and GPS data is consistent with a thrust faulting event. A comparison between the InSAR-observed and GPS-projected line-of-sight (LOS) deformation suggests that descending Sentinel-1 track T046D, descending ALOS-2 track P018D, and ascending ALOS-2 track P112A and GPS data can be used to invert for the source parameters. The results of a nonlinear inversion show that the seismogenic fault is a blind NNW-trending (strike angle ~347.2°), east-dipping (dip angle ~79.6°) thrust fault. On the basis of the optimal fault geometry model, the fault slip distribution jointly inverted from the three datasets reveals that a significant slip area extends 30 km along the strike and 25 km in the downdip direction, and the peak slip magnitude can approach 0.53 m at a depth of 15.5 km. The estimated geodetic moment magnitude released by the distributed slip model is 6.16 ×1018 N⋅m , equivalent to an event magnitude of Mw 6.50, which is slightly smaller than the estimates of focal mechanism solutions. According to the Coulomb stress change at the surrounding faults, more attention should be paid to potential earthquake disasters in this region in the near future. In consideration of the possibility of multi-fault rupture and complexity of regional geologic framework, the refined distributed slip and seismogenic mechanism of this deep reverse faulting should be investigated with multi-disciplinary (e.g., geodetic, seismic, and geological) data in further studies.

Description: To expand the newly developed ARM glasses as reference materials for in situ microanalysis of isotope ratios and iron oxidation state by a variety of techniques such as SIMS, LA-MC-ICP-MS and EPMA, we report Li-B-Si-O-Mg-Sr-Nd-Hf-Pb isotope data and Fe2+/ΣFe ratios for these glasses. The data were mainly obtained by TIMS, MC-ICP-MS, IR-MS and wet-chemistry colorimetric techniques. The quality of these data was cross-checked by comparing different techniques or by comparing the results from different laboratories using the same technique. All three glasses appear to be homogeneous with respect to the investigated isotope ratios (except for B in ARM-3) and Fe2+/ΣFe ratios at the scale of sampling volume and level of the analytical precision of each technique. The homogeneity of Li-B-O-Nd-Pb isotope ratios at the microscale (30–120 μm) was estimated using LA-MC-ICP-MS and SIMS techniques. We also present new EPMA major element data obtained using three different instruments for the glasses. The determination of reference values for the major elements and their uncertainties at the 95% confidence level closely followed ISO guidelines and the Certification Protocol of the International Association of Geoanalysts. The ARM glasses may be particularly useful as reference materials for in situ isotope ratio analysis.

Description: Glaciers are vital to water resources in the arid land of central Asia. Long-term runoff records in the glacierized area are particularly valuable in terms of evaluating glacier recession and water resource change on both a regional and global scale. The runoff records of streams draining basins with 46% current glacier cover, located at the Urumqi Glacier No. 1 in the source area of the Urumqi River in eastern Tianshan, central Asia, were examined for the purpose of assessing climatic and glacial influences on temporal patterns of streamflow for the period 1959–2019. This study has introduced a glacio-hydrologic degree-day model to separate the different hydrologic components in glacier-fed streamflow. Results suggest that runoff from the catchment correlates well with temperature and associated precipitation data. The different ways that the glacier melts in response to temperature versus precipitation in a diurnal scale by changing glacier mass balance can effectively stabilize streamflow, showing a strong capacity of the glacier to naturally adjust streamflow in a beneficial manner to water utilization by those downstream. Based on long-term in-situ observation, we found that the “peak water” of ice melt appeared during the period 1996~2019, which verified the modelling results from previous studies.

Description: The modeled geophysical angular momentum excitation functions (including the contributions of atmosphere, ocean, and hydrology) differ from the geodetic angular momentum excitation function (GAM). The former can simulate historical or forecast data based on the dynamic meteorological models with geodetic observations, while the latter can only get historical data through geodetic techniques such as global navigation satellite system (GNSS), very long baseline interferometry (VLBI), and satellite laser ranging (SLR). Because of potential observational errors and model deficiencies, gaps still exist between the two types of excitation functions in various timescale components. Thus, we must consider the effect of such gaps on the Earth orientation parameters (EOP) prediction. The key to further improving the prediction accuracy of EOP may rest in exploiting specific data processing approaches to address these gaps, so we conduct a detailed study on this issue. We analyze the differences and relations between the two types of excitation functions based on the Earth's rotation equation and its various timescale variational mechanisms. On this basis, we attempt to establish various matching schemes to reduce the gaps between the two types of excitation functions, exploit these schemes in the Earth's polar motion prediction, and compare the prediction results.

Description: The periodic (i.e., ~6-yr, 7-yrs, 8.6-yr) signals in LOD variation were confirmed recently, but their physical mechanisms are still uncertain. Sub-decadal waves inside the fluid outer core (FOC) are also inferred from modern geomagnetic observations. Is there any correlation between these sub-decadal LOD variations and the fast dynamics of Earth’s cores? In this presentation, we will first briefly review the recent findings of the sub-decadal signals in LOD variation, as well as the related geomagnetic observations; Second, we will discuss the potential mechanisms of the ~6-yr and 8.6-yr signals in LOD variation separately. As to the ~6-yr signal, inner core gravitational oscillation plays a key role in its excitation. For the ~8.6-yr LOD signal, it is found to be of very close correspondence with the geomagnetic jerks. To study this interesting phenomenon, we calculated the electromagnetic (EM) torque exerting on the mantle from the azimuthal core surface flow data during 1999-2021, and demonstrate the same ~8.6yr periodic components as those in LOD and good correspondence with the geomagnetic jerks. Next, the LOD change induced by these waves is also estimated in the geostrophic framework and is compared with the LOD observation. All these findings and discussion on their possible relationship and mechanism will be presented.

Description: On February 6, 2023, a sequence of earthquakes with Mw 7.8 and Mw 7.5 occurred in southern central Turkey near the northern border of Syria about in 9 hours. The disastrous earthquake sequence and its other aftershocks caused heavy human casualties and devastating building collapses. We employ the Empirical Orthogonal Function (EOF) analysis to capture coherent spatiotemporal features of co-seismic deformation for three components (N, E, U), which is based on the time series of 1-Hz GPS solutions at 20 permanent stations spatially well-distributed around the ruptured Anatolian fault system. The solved EOF modes show patterns which would help to investigate co-seismic rupture of the seismogenic faults. We compare the EOF-derived co-seismic displacement to the modeling results, which is computed from the spherical, elastic dislocation theory and finite fault model inverted from teleseismic waves records. Both GPS-observed and the modeled displacements show high consistency except for that at station EKZ1 (Ekinözü) where ~4.7 m of westward motion was estimated from GPS which we believe does not entirely represent the crustal motion; some other phenomena such as a local co-seismic landslide or a relative motion of the pillar with respect to the ground might have occurred. Moreover, this sequence is a large typical strike-slip faulting, which can generate gravity change above the threshold proposed by some theoretical simulation based on the satellite gravimetry observations. We also compute forward-modeled coseismic gravity changes, and discuss the plausible detection by instrument onboard of GRACE Follow-On gravimetry mission.

Description: This dataset contains predictions of Earth orientation parameters (EOP) submitted during the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC). The 2nd EOP PCC has been carried out by Centrum Badań Kosmicznych Polskiej Akademii Nauk CBK PAN in Warsaw in cooperation with the GFZ German Research Centre for Geosciences in Potsdam (Germany) and under the auspices of the International Earth Rotation and Reference Systems Service (IERS) within the IERS Working Group on the 2nd EOP PCC. The purpose of the campaign was to re-assess the current capabilities of EOP forecasting and to find most reliable prediction approaches. The operational part of the campaign lasted between September 1, 2021 and December 28, 2022. Throughout the duration of the 2nd EOP PCC, registered campaign participants submitted forecasts for all EOP parameters, including dX, dY, dPsi, dEps (components of celestial pole offsets), polar motion, differences between universal time and coordinated universal time, and its time-derivative length-of-day change. These submissions were made to the EOP PCC Office every Wednesday before the 20:00 UTC deadline. The predictions were then evaluated once the geodetic final EOP observations from the forecasted period became available. Each participant could register more than one method, and each registered method was assigned an individual ID, which was used, e.g., for file naming. The dataset contains text files with predicted parameters as submitted by campaign participants and MATLAB file which is a database with all correct predictions from each participant loaded into a structure.