Temporal aliasing caused by the incomplete reduction of high frequency atmosphere and ocean variability contributes as a major error source in the time-variable gravity field products recovered from the Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow On (GRACE-FO), and likely future gravity missions. The current state-of-the-art of satellite gravity data processing makes use of de-aliasing products to reduce high-frequency mass anomalies, for example, the most recent official Atmosphere and Ocean De-aliasing products (AOD1B-RL06) are applied to model non-tidal mass changes in the ocean and atmosphere. The products already achieved a temporal resolution of 3 hours that greatly improved the quality of gravity inversion compared to the previous releases. In this study, we explore a refined mass integration approach of the atmosphere that considers geometrical, physical, and numerical modifications of the current AOD1B method. Then, the newly available ERA-5 global climate data of 31 km spatial and 1-hour temporal resolution are used to produce a new set of non-tidal atmosphere de-aliasing product (HUST-ERA5) that is computed in terms of spherical harmonics up to degree/order 100 covering 2002 onwards. Despite of an overall agreement with the AOD1B-RL06 (correlation of low-degree coefficients are all greater than 0.99), discrepancy is still distinguished for spatial-temporal analysis, i.e., a better consistency of HUST-ERA5 from 2007 to 2010. The factors contributing the differences, including the input data, method and temporal resolution, are therefore respectively analyzed and quantified through extensive assessments. We find the difference of HUST-ERA5 and AOD1B-RL06 has led to a mean variation of 7.34 nm/s on the the LRI (Laser Ranging Interferometry) range-rate residual on Jan 2019, which is close to the LRI precision already. This impact is invisible for GRACE(-FO) gravity inversion because of the less accurate onboard KBR(K-band ranging) instrument, however, it will be nonnegligible and should be considered when the LRI completely replaces KBR in the future gravity mission. In addition, HUST-ERA5 can also be widely used in LEO satellite orbit determination and superconducting gravimeter atmospheric correction.
YANG Fan, LUO Zhicai
These datasets fill the data gap between GRACE and GRACE-FO, they contain CSR RL06 Mascon and JPL RL06 Mascon. They take China as the study area, and the dataset includes "Decimal_time”, "lat”, "lon”, "time”, "time_bounds”, "TWSA_REC" and "Uncertainty" 7 parameters in total. Among them, "Decimal_time” corresponds to decimal time. There are 191 months from April 2002 to December 2019 (163 months for GRACE data, 17 months for GRACE-FO data, and 11 months for the gap between GRACE and GRACE-FO. We have not filled the missing data of individual months between GRACE or GRACE-FO data). "lat" corresponds to the latitude range of the data; "lon" corresponds to the longitude range of the data; "time" corresponds to the cumulative day of the data from January 1, 2002. And "time_bounds" corresponding to the cumulative day at the start date and end date of each month. “TWSA_REC" represents the monthly terrestrial water storage anomalies from April 2002 to December 2019 in China; "Uncertainty" is the uncertainty between the data and CSR RL06 Mascon products. We use GRACE satellite data from CSR GRACE/GRACE-FO RL06 Mascon solutions (version 02), China Gauge-based Daily Precipitation Analysis (CGDPA, version 1.0) data, and CN05.1 temperature dataset. The precipitation reconstruction model was established, and the seasonal and trend terms of CSR RL06 Mascon products were considered to obtain the dataset of terrestrial water storage anomalies in China. The data quality is good as a whole, and the uncertainty of most regions in China is within 5cm. This dataset complements the nearly one-year data gap between GRACE and GRACE-FO satellites, and provides a full time series for long-term land water storage change analysis in China. As the CSR RL06 Mascon product, the average value between 2004.0000 and 2009.999 is deducted from this dataset. Therefore, the 164-174 months (i.e., July 2017 to May 2018) of this dataset can be directly extracted as the estimation of terrestrial water storage anomalies during the gap period. The reconstruction method for the gap of JPL RL06 Mascon is consistent with that of CSR RL06 Mascon.
ZHONG Yulong, FENG Wei, ZHONG Min, MING Zutao
The dataset is the teleseismic waveform data from the Gyirong – Peiku Tso short-period dense seismic array profile. The data can be used to receiver function methods to probe the structure of the crust and upper mantle. The Gyirong – Peiku Tso profile crosses the north-south Gyirong Rift, and the data are derived from 134 short-period seismic stations set up by the subject group along the east-west Gyirong – Peiku Tso profile, with strict site selection and good data quality. This profile provides an important scientific basis for revealing the velocity discontinuity morphology below the Chilung Rift Valley, i.e., the interfacial extension of the Indian continent swooping northward in the crust below the Himalayan zonation, and for further understanding the lateral changes of the MHT interface and the dynamics of the east-west extension of the Tibetan Plateau.
We compiled the Seismotectonic Map of Western Asia using the ArcGIS platform through data collecting and digitization. The seismotectonic map of Western Asia covers Iran and its surrounding countries and regions. Based on the “Major active faults of Iran” map, the seismotectonic map is replenished with massive published data and depicts the location and nature of the seisogenic faults or active faults and the epicenter of earthquakes with M ≥ 5 from 1960 to 2019. The map can not only be used in the research of active faults and seismic risks in Western Asia, but also will be applied to the seismic safety evaluation for infrastructure construction.
The Pan-Third Polar region has strong seismic activity, which is driven by the subduction and collision of the Indian plate, the Arab plate and the Eurasian plate. 18806 earthquakes with Magnitude 5 or larger have occurred in Pan-Third Polar region (north latitude 0-56 degrees and east longitude 43-139 degrees) since 1960. Among them, 4 earthquakes with Magnitude 8 or larger, 187 earthquakes with Magnitude 7.0-7.9， 1625 earthquakes with Magnitude 6.0-6.9 and 16990 earthquakes with Magnitude 5.0-5.9 have occurred. Earthquakes occurred mainly in the foothills of the India-Myanmar Mountains, the Himalaya Mountains, the Sulaiman Mountains, where the India Plate collided with the Eurasian plate, and the Zagros Mountains where the Arab plate collided with the Eurasian plate.
We compiled the Seismic Zonation Map of Western Asia using the ArcGIS platform through data collecting and digitization. The Seismic Zonation map of Western Asia covers Iran and its surrounding countries and regions. Based on the “Major active faults of Iran” map, the map is replenished with massive published data and depicts the location and nature of the seisogenic faults or active faults and the epicenter of earthquakes with M ≥ 5 from 1960 to 2019. The zonation map shows the mean values of peak ground acceleration (PGA) with 10% probability of being exceeded in 50 years. The two maps can not only be used in the research of active faults and seismic risks in Western Asia, but also will be applied to the seismic safety evaluation for infrastructure construction.
This data comes from the result of teleseismic data, mainly including the velocity and radial anisotropic structures beneath western Tibet. In the process of processing, bandwidth filtering is adopted, and the filtering range is 0.05-2 Hz. Due to the use of teleseismic data, the cross-correlation method is used in the acquisition process to "align" the waveform. The data quality is good, because the extracted data are all from the earthquakes with magnitude greater than 5.0 located in the global seismic catalog, and each event has an obvious take-off point. The data can be used by other seismologists to reconstruct and analyze the underground structures in this area.
The 2015 Gorkha, Nepal earthquake (Mw 7.8) ruptured the Main Himalayan Thrust (MHT) and allows direct measurements of the behavior of the continental collision zone. We study the MHT using seismic waveforms recorded by local stations that completely cover the aftershock zone (Event catalog 1.docx and Event catalog 2.docx). We obtained the velocity structure beneath the study zone (Velocity.dat). The MHT exhibits clear lateral variation along geologic strike, with the Lesser Himalayan ramp having moderate dip on the MHT beneath the mainshock area and a flatter and deeper MHT beneath the eastern end of the aftershock zone. East of the aftershock zone, seismic wave speed increases at MHT depths, perhaps due to subduction of an Indian basement ridge. A similar magnitude wave speed change occurs at the western end of the aftershock zone. These gross morphological structures of the MHT controlled the rupture length of the Gorkha earthquake.
We use waveform cross-correlation to analyze the recordings of eight earthquakes (2009-2018) beneath the Indian Ocean at stations from the Chinese Digital Seismic Network. We obtain 929 high quality residual traveltime differences between the phases ScS and S (Differential traveltimes.dat). We interpret variations of δt up to 10 seconds as due to horizontal shear-velocity variations in D” beneath northern India, Nepal, and southwestern China. The shear velocity can vary by as much as 7% over distances shorter than 300 km. Our observations provide additional observational evidence that compositional heterogeneity and possibly melt contribute to the seismic structure of the lower mantle characterized by long-term subduction and mantle downwelling.
LI Guohui, BAI Ling
This data set is collected from the supplementary information part of the paper: Pei, S.P., Niu, F.L., Ben-Zion, Y., Sun, Q., Liu, Y.B., Xue, X.T., Su,J.R., & Shao, Z.G. (2019). Seismic velocity reduction and accelerated recovery due to earthquakes on the Longmenshan fault. Nature Geoscience. 12. 387-392. doi:10.1038/s41561-019-0347-1. This paper studies the structural evolution process of The Longmenshan fault zone located at a pronounced topographic boundary between the eastern margin of the Tibetan plateau and the western Sichuan basin. With the observations on coseismic velocity reductions and the healing phases, it is found that the healing phase of Wenchuan earthquake fracture zone accelerated significantly in response to the Lushan earthquake. This data set contains 3 tables, table names and content are as follows: Data list: The data name list of the rest tables; t1: Data of the four periods (befor Wenchuan earthquake, after Wenchuan earthquake, before Lushan earthquake, after Lushan earthquake); t2: The average velocities with error in Figure 2 in the paper for Wenchuan earthquake (WCEQ) and Lushan earthquake (LSEQ) area. See attachments for data details: Supplementary information.pdf, Seismic velocity reduction and accelerated recovery due to earthquakes on the Longmenshan fault.pdf.
The dataset partially used in the study of paper 2018GC007986 includes S receiver functions derived from 48 permanent stations and 11 stations of a temporary HY array deployed in the northeastern Tibetan Plateau. The dataset as a zipped file contains one folder, two files including NETibet_SRF.QBN and NETibet_SRF.QHD. A spiking deconvolution in the time domain is used to calculate the P and S receiver functions, all the S receiver functions have been visually inspected to remove the bad traces that obviously different from the majority. The dataset is applied to explore the lithospheric structure and understand the mechanism of northeastern expansion and growth of NE Tibetan Plateau.
On Nov. 18 at 06:34 CST time, an M6.9 earthquake occurred at Mainling prefecture, Nyingchi City, Tibet. This earthquake is located close to the northeastern corner where the Indian plate underthrusts beneath the Eurasian plate. Here the crustal shortening and the tectonically rotated deformation are the strongest with respect to other areas along the whole Himalayan orogenic belt. To record the seismic waveforms, we deployed seismic stations. Due to the huge amount of original waveform data, this database include waveforms of earthquakes with magnitudes greater than 3 that occurred between November 18, 2017 and December 31, 2018.
High-frequency continuous GPS observation can effectively monitor the kinematics of crustal deformation. The Qilian Mountains region is an important constraint boundary of the northeastern margin of the Qinghai-Tibet Plateau. The study of this region can provide important implications for the dynamic process of the growth and uplift of the Tibetan Plateau and the internal deformation of the Tibetan Plateau. At the local level, it can be discussed whether there is creepage in the Haiyuan fault and the movement mode of the northeastern margin of the Qinghai-Tibet Plateau. The data comes from 26 fixed stations set up by the research group in the Qilian Mountain area. The site selection requirements are strict, and the high-frequency continuous GPS receiver is Provided by trimble, the data quality is good, the data can be applied not only to geodynamic research, but also to related earth science research such as meteorological precipitation.
The Pan-Third Polar region has strong seismic activity, which is driven by the subduction and collision of the Indian plate, the Arab plate and the Eurasian plate. 3809 earthquakes with Magnitude 6 or larger have occurred in Pan-Third Polar region (north latitude 0-56 degrees and east longitude 43-139 degrees) since 1960. Among them, 59 earthquakes with Magnitude 8 or larger, 689 earthquakes with Magnitude 7.0-7.9 and 3061 earthquakes with Magnitude 6.0-6.9 have occurred. Earthquakes occurred mainly in the foothills of the India-Myanmar Mountains, the Himalaya Mountains, the Sulaiman Mountains, where the India Plate collided with the Eurasian plate, and the Zagros Mountains where the Arab plate collided with the Eurasian plate.
Under the background of global warming, over the past few decades the qinghai-tibet plateau lakes shows obvious extension. At present on the qinghai-tibet plateau lakes area increase sharply , such as water level changes reported by a number of studies, especially in Tibet's largest lakes such as Siling Co, Nam Co, and so on. We take the Nam Co lake as an example, discussed recent decades the non-structural loading force caused by the Nam Co water level rising result in the surrounding lithosphere deformation and the stress variation on the Yadong-Gulu fault zone (normal fault) and analysis of the seismic hazard. In this fragile ecological environment area, the relationship between the land surface processes and the lithosphere can give us some clues, the result of the data including the surface displacement field changes and the stress on the fault.