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: 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: 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: On 2015 November 4, an Mw 6.5 earthquake struck the east region of Alor Island, eastern Indonesia. Here, we use Sentinel-1 and ALOS-2 data to explore the coseismic surface displacement of this earthquake. Based on the ALOS-2 coseismic interferograms, the first fault model and coseismic slip distribution of the 2015 Alor earthquake are presented in this study. The preferred slip model links to a blind south-southeast striking, south-southwest dipping strike-slip fault with amount of normal slip component and a peak slip of 2.09 m at 2.34 km of depth. Considering the fact that the ascending and descending InSAR prediction of the distributed slip model does not fit the InSAR observations at the northwest and southeast tips with the simple planar fault model. We tried to construct a strike-variable fault model to further improve data fit. The results of the calculated Coulomb stress change imply that the regions with positive CFS changes mainly located at the northwest and southeast extremities of the rupture of the Alor earthquake, and in the lobes north and south of the rupture. The most striking discovery from the InSAR observations of the Alor earthquake is that most of the displacements occurred on a fault whose existence was unknown before the earthquake.

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.

Description: The China Earthquake Administration established a network for intensity rapid report and earthquake early warning (IRREEW) in 2016–2020, which consists of approximately 5000 conventional strong‐motion and approximately 10,000 low‐cost micro‐electro‐mechanical system (MEMS) seismometers. These seismographs, particularly MEMS stations, can provide a large amount of near‐field waveform data suitable for rapid source inversion. Compared with conventional strong‐motion data, MEMS recordings have rarely been used in the previous source inversions, because the MEMS technology is newly applied in earthquake monitoring, and the seismograph has a relatively lower signal‐to‐noise ratio and more severe baseline shifts. However, from waveform comparisons at collocated MEMS and strong‐motion stations, we find that they are highly consistent with each other, particularly at frequencies above 0.04 Hz. To explore the application prospect of MEMS data to source inversion, we inverted both MEMS and strong‐motion data for three strong earthquakes recorded by the IRREEW network during 2021–2022 to determine their rupture processes. In applications to the 2021 Mw 6.1 Yangbi earthquake, the 2022 Mw 6.6 Menyuan earthquake, and the 2022 Mw 6.6 Luding earthquake, the MEMS data equally well constrain the rupture model. The resulting source information, including the moment magnitude, rupture direction, and rupture dimension, are consistent with those obtained from the strong‐motion inversions. Because the low‐cost MEMS instruments can be deployed densely around seismically active regions, they can provide urgent waveform data for rapid determination of rupture process, which is crucial for simulation of strong ground motions, and assessments of earthquake and related disasters.

Description: The intraplate Hawaiian-Emperor Seamount Chain has long been considered a hotspot track generated by the motion of the Pacific plate over a deep mantle plume, and an ideal feature therefore for studies of volcanic structure, magma supply, plume-crust interaction, flexural loading, and upper mantle rheology. Despite their importance as a major component of the chain, the Emperor Seamounts have been relatively little studied. In this paper, we present the results of an active-source wide-angle reflection and refraction experiment conducted along an ocean-bottom-seismograph (OBS) line oriented perpendicular to the seamount chain, crossing Jimmu guyot. The tomographic P wave velocity model, using ∼20,000 travel times from 26 OBSs, suggests that there is a high-velocity (〉6.0 km/s) intrusive core within the edifice, and the extrusive-to-intrusive ratio is estimated to be ∼2.5, indicating that Jimmu was built mainly by extrusive processes. The total volume for magmatic material above the top of the oceanic crust is ∼5.3 × 104 km3, and the related volume flux is ∼0.96 m3/s during the formation of Jimmu. Under volcanic loading, the ∼5.3-km-thick oceanic crust is depressed by ∼3.8 km over a broad region. Using the standard relationships between Vp and density, the velocity model is verified by gravity modeling, and plate flexure modeling indicates an effective elastic thickness (Te) of ∼14 km. Finally, we find no evidence for large-scale magmatic underplating beneath the pre-existing crust.