Automated GNSS and Teleseismic Earthquake Inversion (AutoQuake Inversion) for Tsunami Early Warning: Retrospective and Real-Time Results

Rapid finite fault source determination is critical for reliable and robust tsunami early warnings. Near-field Global Navigation Satellite System (GNSS) observations have shown value to constrain the source inversion, but real-time GNSS stations are sparse along most of the active faults. Here we propose an automatic earthquake finite source inversion (AutoQuake Inversion) algorithm jointly using near-field (epicentral distance < 1000 km) GNSS data and mid-range (epicentral distance from 30° to 45°) teleseismic P displacement waveforms. Neither the near-field GNSS nor the mid-range teleseismic data clip or saturate during large earthquakes, while the fast-traveling P-waves are still essential to constrain the source in regions where very few or no GNSS stations are available. Real-time determination of the fault geometry remains to be the main challenge for rapid finite source inversion. We adopt a strategy to use the pre-defined geometry Slab2 for earthquakes within it or to forecast a focal mechanism based on near-by historical events for earthquakes without Slab2 prior. The algorithm has been implemented successfully in the prototype of JPL’s GPS-Aided Tsunami Early-Detection system and tested for many real events recently. This article provides the framework of the algorithm, documents the retrospective and real-time results, and discusses remaining challenges for future improvements

Automated GNSS and Teleseismic Earthquake Inversion (AutoQuake Inversion) for Tsunami Early Warning: Retrospective and Real-Time Results

Rapid finite fault source determination is critical for reliable and robust tsunami early warnings. Near-field Global Navigation Satellite System (GNSS) observations have shown value to constrain the source inversion, but real-time GNSS stations are sparse along most of the active faults. Here we propose an automatic earthquake finite source inversion (AutoQuake Inversion) algorithm jointly using near-field (epicentral distance < 1000 km) GNSS data and mid-range (epicentral distance from 30° to 45°) teleseismic P displacement waveforms. Neither the near-field GNSS nor the mid-range teleseismic data clip or saturate during large earthquakes, while the fast-traveling P-waves are still essential to constrain the source in regions where very few or no GNSS stations are available. Real-time determination of the fault geometry remains to be the main challenge for rapid finite source inversion. We adopt a strategy to use the pre-defined geometry Slab2 for earthquakes within it or to forecast a focal mechanism based on near-by historical events for earthquakes without Slab2 prior. The algorithm has been implemented successfully in the prototype of JPL’s GPS-Aided Tsunami Early-Detection system and tested for many real events recently. This article provides the framework of the algorithm, documents the retrospective and real-time results, and discusses remaining challenges for future improvements

Scientific Impacts of Wind Direction Errors

An assessment on the scientific impact of random errors in wind direction (less than 45 deg) retrieved from space-based observations under weak wind (less than 7 m/s ) conditions was made. averages, and these weak winds cover most of the tropical, sub-tropical, and coastal oceans. Introduction of these errors in the semi-daily winds causes, on average, 5% changes of the yearly mean Ekman and Sverdrup volume transports computed directly from the winds, respectively. These poleward movements of water are the main mechanisms to redistribute heat from the warmer tropical region to the colder high- latitude regions, and they are the major manifestations of the ocean's function in modifying Earth's climate. Simulation by an ocean general circulation model shows that the wind errors introduce a 5% error in the meridional heat transport at tropical latitudes. The simulation also shows that the erroneous winds cause a pile-up of warm surface water in the eastern tropical Pacific, similar to the conditions during El Nino episode. Similar wind directional errors cause significant change in sea-surface temperature and sea-level patterns in coastal oceans in a coastal model simulation. Previous studies have shown that assimilation of scatterometer winds improves 3-5 day weather forecasts in the Southern Hemisphere. When directional information below 7 m/s was withheld, approximately 40% of the improvement was los

Ionospheric Signatures of Tohoku-Oki Tsunami of March 11, 2011: Model Comparisons Near the Epicenter

We observe ionospheric perturbations caused by the Tohoku earthquake and tsunami of March 11, 2011. Perturbations near the epicenter were found in measurements of ionospheric total electron content (TEC) from 1198 GPS receivers in the Japanese GEONET network. For the first time for this event, we compare these observations with the estimated magnitude and speed of a tsunami-driven atmospheric gravity wave, using an atmosphere-ionosphere-coupling model and a tsunami model of sea-surface height, respectively. Traveling ionospheric disturbances (TIDs) were observed moving away from the epicenter at approximate speeds of 3400 m/s, 1000 m/s and 200–300 m/s, consistent with Rayleigh waves, acoustic waves, and gravity waves, respectively. We focus our analysis on gravity waves moving south and east of the epicenter, since tsunamis propagating in the deep ocean have been shown to produce gravity waves detectable in ionospheric TEC in the past. Observed southeastward gravity wave perturbations, seen 60 min after the earthquake, are mostly between 0.5 to 1.5 TECU, representing up to 5% of the background vertical TEC (VTEC). Comparisons of observed TID gravity waves with the modeled tsunami speed in the ocean and the predicted VTEC perturbation amplitudes from an atmosphere-ionosphere-coupling model show the measurements and models to be in close agreement. Due to the dense GPS network and high earthquake magnitude, these are the clearest observations to date of the effect of a major earthquake and tsunami on the ionosphere near the epicenter. Such observations from a future real-time GPS receiver network could be used to validate tsunami models, confirm the existence of a tsunami, or track its motion where in situ buoy data is not available

A Feasibility Study of Three-Dimensional Empirical Orthogonal Functions From the NASA JPL Ocean General Circulation Model: Computing, Visualization and Interpretation

Existing oceanic studies on either data reconstruction or dynamics often used 2-dimensional empirical orthogonal functions (EOF) for sea surface temperature (SST) and for deep layers. However, large-scale oceanic dynamics, such as equatorial ocean upwelling and arctic ocean ventilation, imply the existence of strong covariance among the temperatures and other parameters between different layers. These ocean dynamics are not best represented in the isolated 2-dimensional layer-by-layer calculations, while the 3-dimensional EOFs have a clear advantage. The purpose of this paper is to demonstrate 3D EOF calculations based on the NASA Jet Propulsion Laboratory (JPL) ocean general circulation model (OGCM) from surface to 5,500 meters depth, with 33 depth layers, 1-degree latitude and longitude spatial resolution, and monthly temporal resolution. We also present visualizations of the 3D EOFs and make physical interpretations of the first two EOFs. Our 3D EOF results demonstrate that (i) the 3D spatial pattern of equatorial ocean upwelling is mainly reflected in the first EOF mode and has its most variabilities within the depth layer between 100 and 400 meters, (ii) the 3D El Niño Southern Oscillation (ENSO) dynamic pattern is mainly reflected in the second EOF mode and is mostly confined from surface to the depth of 150 meters, and (iii) the lead eigenvalue from the 3D EOF calculation appears to contain some signal of oceanic warming. Additionally, our method of weighted 3D EOF computation and our 3D visualization Python code may be useful tools for both climate professionals and students

Triggering of the Mw 7.2 Hawaii earthquake of May 4, 2018 by a dike intrusion

A Mw 7.2 earthquake struck the south flank of Kilauea, Hawaii, on 4 May 2018, following a period of volcanic unrest. To investigate its relationship with the stress changes induced by prior tectonic and magmatic activity, we model the coseismic slip distribution, preintrusion deformation, and dike intrusion using geodetic, seismic, and tsunami observations. The décollement beneath the south flank was creeping seaward by ~25 cm/year. Diking started on 20 April and led to fissure eruption on 3 May. The magmatic activity and creep resulted in an onshore U‐shaped zone of stress unloading, fringed by an off‐shore zone of stress buildup that apparently guided the 2018 rupture. It takes only 20 to 35 years at the preintrusion rate to accumulate a moment deficit equivalent to the moment that was released in 2018. This event falls short of balancing the moment budget since the 1975 Mw 7.7 earthquake

Triggering of the Mw 7.2 Hawaii earthquake of May 4, 2018 by a dike intrusion

A Mw 7.2 earthquake struck the south flank of Kilauea, Hawaii, on 4 May 2018, following a period of volcanic unrest. To investigate its relationship with the stress changes induced by prior tectonic and magmatic activity, we model the coseismic slip distribution, preintrusion deformation, and dike intrusion using geodetic, seismic, and tsunami observations. The décollement beneath the south flank was creeping seaward by ~25 cm/year. Diking started on 20 April and led to fissure eruption on 3 May. The magmatic activity and creep resulted in an onshore U‐shaped zone of stress unloading, fringed by an off‐shore zone of stress buildup that apparently guided the 2018 rupture. It takes only 20 to 35 years at the preintrusion rate to accumulate a moment deficit equivalent to the moment that was released in 2018. This event falls short of balancing the moment budget since the 1975 Mw 7.7 earthquake

Photoconductivity of biased graphene

Graphene is a promising candidate for optoelectronic applications such as photodetectors, terahertz imagers, and plasmonic devices. The origin of photoresponse in graphene junctions has been studied extensively and is attributed to either thermoelectric or photovoltaic effects. In addition, hot carrier transport and carrier multiplication are thought to play an important role. Here we report the intrinsic photoresponse in biased but otherwise homogeneous graphene. In this classic photoconductivity experiment, the thermoelectric effects are insignificant. Instead, the photovoltaic and a photo-induced bolometric effect dominate the photoresponse due to hot photocarrier generation and subsequent lattice heating through electron-phonon cooling channels respectively. The measured photocurrent displays polarity reversal as it alternates between these two mechanisms in a backgate voltage sweep. Our analysis yields elevated electron and phonon temperatures, with the former an order higher than the latter, confirming that hot electrons drive the photovoltaic response of homogeneous graphene near the Dirac point

The Efficacy, Safety, and Immunogenicity of Switching Between Reference Biopharmaceuticals and Biosimilars: A Systematic Review

To date, no consensus exists among stakeholders about the safety of switching between reference biological products (RPs) and biosimilars, which may have been curbing the implementation of biosimilars in clinical practice. This study synthesizes the available data on switching and assesses whether switching patients from a RP to its biosimilar or vice versa affects efficacy, safety, or immunogenicity outcomes. A total of 178 studies, in which switch outcomes from a RP to a biosimilar were reported, was identified. Data were derived from both randomized controlled trials and real-world evidence. Despite the limitations stemming from a lack of a robust design for most of the studies, the available switching data do not indicate that switching from a RP to a biosimilar is associated with any major efficacy, safety, or immunogenicity issues. Some open-label and observational studies reported increased discontinuation rates after switching, which were mainly attributed to nocebo effects. Involvement of the prescriber in any decision to switch should remain and attention should be paid to the mitigation of a potential nocebo effect