ALBERT

Description: The intrusion of igneous sills into organic-rich sediments accompanies the emplacement of igneous provinces, continental rifting, and sedimented seafloor spreading. Heat from intruding sills in these settings alters sedimentary organic carbon, releasing methane and other gasses. Recent studies hypothesize that carbon released by this mechanism impacts global climate, particularly during large igneous province emplacements. However, the direct impacts of sill intrusion, including carbon release, remain insufficiently quantified. Here, we present results from International Ocean Discovery Program (IODP) Expedition 385 comparing drill-core and wireline measurements from correlative sedimentary strata at adjacent sites cored in Guaymas Basin, Gulf of California, one altered by a recently intruded sill and one unaffected. We estimate 3.30 Mt of carbon were released due to this sill intrusion, representing an order of magnitude less carbon than inferences from outcrops and modeling would predict. This attenuated carbon release can be attributed to shallow intrusion and the high heat capacity of young, high-porosity sediments. Shallow intrusion also impacts sub-seafloor carbon cycling by disrupting advective fluxes, and it compacts underlying sediments, increasing potential carbon release in response to subsequent intrusions.

Description: Integrated processing of high-rate GNSS and accelerometer data can overcome the disadvantage of each individual sensors and to increase the quality of derived co-seismic displacement. However, the contribution of accelerometer is usually underestimated by estimating baseline shifts epoch-wise which in fact happened very rarely. To take full advantage of both sensors, we propose a sliding window based Kalman filter to detect baseline shifts according to the disagreement of GNSS and accelerometer data and to estimate only the detected baseline shifts. The relationship of the window width, minimal detectable baseline shift and the displacement accuracy is investigated. The performance of the proposed approach is demonstrated by datasets collected during Samos Island earthquake (Mw 7.0, 30th October 2020). The results show that the baseline shifts in accelerometers can be precisely detected and estimated according to the very good agreement of the displacement integrated from accelerometer data after applying baseline shift corrections and that estimated from high-rate GNSS. Furthermore, the baseline corrected accelerometer data provides tight and reliable constraints on position and velocity to facilitate correct PPP ambiguity resolution. Thanks to the proposed approach, the complementary of GNSS and accelerometers is fully employed, consequently the co-seismic displacements of the tightly integrated processing are significantly improved.

Description: Recent advances in high-precision real-time applications of the Global Navigation Satellite System (GNSS) have expanded to monitoring and early detection of natural hazards. The real-time Precise Point Positioning with Regional Augmentation (PPP+RA) technique has become increasingly popular for providing rapid and precise ground displacement information due to the availability of real-time precise GNSS satellite orbit and clock products, as well as high-rate observations. In this contribution, we implemented the PPP+RA technique to the Early-Warning and Rapid Impact Assessment with real-time GNSS in the Mediterranean (EWRICA) project for earth surface displacement monitoring. A real-time GNSS precise positioning system is developed for the project. About 80 stations from the RING network in Italy are used to evaluate the performance the system. It's worth noting that more than half of the receivers in the RING network are LEICA receivers that support GPS only. We use GFZ’s real-time precise satellite orbit and clock products for the data processing. The results show that the daily averaged accuracy of PPP+RA is 1.08 cm, 1.15 cm, and 3.20 cm in the east, north, and up directions, respectively, with a Time To First Fix (TTFF) of 1.1 minutes. Additionally, the system provides short-term relative positioning accuracy within 10 minutes, with a precision of a few millimetres, demonstrating its capability to detect even slight ground movements in real-time.

Description: The INGV RING research infrastructure is based on a permanent GNSS network developed to measure deformation at different spatial and temporal scales in the Mediterranean region. The network (http://ring.gm.ingv.it/) consists of ~250 real-time transmitting remote sites, using standard RTCM format, towards the Irpinia acquisition centres (Southern Italy). Data streaming is managed by a Ntrip Caster (https://igs.bkg.bund.de/ntrip/bkgcaster), whose sourcetable is synchronized with the RING database, thus guaranteeing reliable metadata for the analysis. Within the EWRICA project, the real-time data analysis is performed by using the RTPPP software (Ge et al.,2012) that provides different Precise Point Positioning products with increasing accuracies (standard PPP, PPP-AR and PPP-RA). On 24-h data, the ambiguity resolution (PPP-AR) and the regional augmentation (PPP-RA) allows accuracies of ~1 cm and ~3 cm for the horizontal and vertical components, respectively, at the best sites. Using shorter sliding windows (i.e. 60 s or 120 s, thus simulating a real-time situation), the accuracies are ~0,5 cm and ~1 cm for horizontal and vertical components, respectively. We also tested a homemade algorithm able to detect co-seismic static offsets in real-time in a simulated real-time strategy. The first results make the RING real-time solutions a potential contribution to be tested in earthquake and tsunami warning systems in Italy and surrounding regions. We will show the RING architecture, from the data to the PPP results, an evaluation of the uncertainties, and some examples of offset detection for recent earthquakes.

Description: High-precision real-time GNSS have recently expanded to monitoring and early detection of natural hazards. German research project EWRICA (Early-Warning and Rapid ImpaCt Assessment with real-time GNSS in the Mediterranean) funded by the national Ministry for Education and Research aims for the prototype implementation of the GNSS-augmented seismic source inversion and rapid impact assessment in the seismically active regions of Mediterranean. The project runs in close cooperation with partners operating high-rate GNSS networks RING (Italy) and NOANET (Greece). An overarching goal is to compute robust local ground motion models shortly after an earthquake to assess areas of strong shaking as well as secondary effects such as tsunamis and landslides. The four work packages - (1) real-time processing of coseismic displacements (RT-multi GNSS with regional augmentation, streamed in miniSEED format via SeedLink server, optionally joint processing with collocated accelerometers); (2) fast source inversion (Bayesian moment-tensor solution with Pyrocko tools); (3) rapid impact assessment (neural network predictions of ground motion maps with uncertainties, also coupled to probabilistic tsunami forecasting PTF at INGV); and (4) system prototype -- end up with an operational system prototype to demonstrate the full operational processing chain by hindcasting selected historical (e.g., 2016 M6.2 Norcia; 2020 M7 Samos) and synthetic event scenarios. EWRICA may serve as a blueprint for other regions of the world: currently EWRICA's tools are being tested for application in Indonesia, together with the colleagues from the Geospatial Agency (BIG) and from the national tsunami warning center InaTEWS.

Description: Real-time satellite clock offset is a crucial element for real-time precise point positioning (RT-PPP). However, the elapsed time for undifferenced (UD) multi-global navigation satellite system (GNSS) real-time satellite clock offset estimation at each epoch is increased with the growth of stations, which may fall short of real-time application requirements. Therefore, a rapid estimation method for UD multi-GNSS real-time satellite clock offset is proposed to improve the computation efficiency, in which both the dimension of the normal equation (NEQ) and the number of redundant observations are calculated before adjustment; if these two values are larger than the predefined thresholds, the elevation mask is gradually increased until they are less than the predefined thresholds. Then, the clock offset estimation is conducted; this method is called clock offset estimation using partial observations. Totals of 50, 60, 70 and 80 stations are applied to perform experiments. Compared to clock offset estimation using all observations, the elapsed times of clock offset estimation using partial observations can be reduced from 6.80 to 3.10 s, 7.93 to 2.97 s, 12.04 to 3.14 s for 60, 70 and 80 stations, respectively. By using the proposed method, the elapsed time of the clock offset estimation at each epoch is less than 5 s. The estimated clock offset accuracy for GPS, BDS-3, Galileo and GLONASS satellites are better than 0.04, 0.05, 0.03 and 0.16 ns when using the partial observations to estimate clock offset with 50, 60, 70 and 80 stations, respectively. For the multi-GNSS kinematic PPP using the estimated clock offset from 50, 60, 70 and 80 stations with partial observations, the positioning accuracy at 95% confidence level in the east, north and up direction are better than 2.70, 2.20 and 5.60 cm, respectively.