Gabriele Colosimo

GPS Near-Real-Time Coseismic Displacements for the Great Tohoku-oki Earthquake

Here, we present the application to the great Tohoku-oki (Japan) earthquake (United States Geological Survey M = 9.0, March 11, 2011, 05:46:24 Coordinated Universal Time) of a novel approach, named Variometric Approach for Displacements Analysis Stand-Alone Engine, able to estimate accurate coseismic displacements and waveforms in real time, in the global reference frame, just using the standard broadcast products (orbits and clocks) and the high-rate (1 Hz or more) carrier phase observations continuously collected by a stand-alone global-positioning-system receiver. We processed separately the data collected at MIZU (Mizusawa, 140 km from the epicenter) and USUD (Usuda, 430 km from the epicenter) International Global Navigation Satellite System Service sites. A total horizontal displacement of about 2.4 m east-southeast was estimated for the MIZU, with a maximum horizontal oscillation amplitude of about 3.4 m along the same direction. Generally, an overall accuracy better than 10 cm for all the components (east, north, and up) and an average accuracy around 5 cm were assessed over an interval shorter than 5 min, with respect to independent solutions obtained with two different scientific software. The threshold of 5-cm accuracy has been recently indicated as sufficient for real-time fault determination for near-field tsunami forecasting for a major earthquake, like the 2011 Tohoku-oki one.

GeoEye-1: Analysis of Radiometric and Geometric Capability

The Geoeye-1 satellite, launched in September 2008, is able to acquire imagery in panchromatic mode, with a spatial resolution of 0.41 m at nadir, offering the most powerful way to obtain detailed imagery actually commercially available.

Global and local reference frames

The goal of this review paper is to recall the concept of geodetic reference frame, showing its intrinsic dependence from all the information and choices related to its realization, and to discuss the still alive distinction between “global” and “local” reference frames, considering the unbreakable link between Geodesy and Geophysics. An up-to-date review of the most relevant presently adopted global and local (in this respect, mainly at European and Italian level) reference frames is presented. Finally, some conclusions and still open problems, related to the current research, are outlined.

VADASE: State of the Art and New Developments of a Third Way to GNSS Seismology

In recent years, extensive work has been done to effectively exploit Global Navigation Satellite Systems (GNSS) for estimating important earthquake parameters such as the seismic moment and magnitude (i.e. GNSS Seismology). The rapid and accurate assessment of these parameters is of crucial importance to achieve reliable tsunami generation scenarios and eventually dispatch an early warning. In this framework, Geodesy and Geomatics division (AGG) of Sapienza University of Rome developed a new approach to obtain in real-time the 3D displacements of a single GNSS receiver. This solution, called VADASE (Variometric Approach for Displacement Analysis Standalone Engine), utilizes the broadcast orbits and the time differences of the high-rate (i.e. 1 Hz or more) carrier phases observations to ascertain the receiver movements over short intervals at a few centimeters accuracy level in real-time.

The variometric approach to real-time high-frequency geodesy

AbstractHigh-frequency geodesy is here intended as the capability of retrieving information relevant to geodesy and geophysics at high frequency through geodetic measurements and methodologies. In particular, this short review work focuses on two aspects: fast ground motions, as those due to earthquakes, and fast ionospheric total electron content (TEC) disturbances, as those caused by tsunamis. This information can be retrieved, even in real time, from Global Navigation Satellite System observations collected at high rate (equal or higher than 1 Hz), and can significantly support geohazard understanding contributing in seismic moment estimation and tsunami early warning. Here, the real-time possibilities of the new variometric approach for high-frequency geodesy are summarized: the fundamental idea is to directly focus on the quantities of interest, which are “variations” (of positions, of ionospheric TEC) and can be properly estimated in real time. The work moves “from ground to ionosphere”: with respect to the ground, the more consolidated application of the variometric approach to GNSS seismology (VADASE) is presented, up to the latest developments; with respect to the ionosphere, the brand new application named VARION for TEC disturbances computation is described, and the first results of the application to the Illapel, Chile earthquake (USGS

RADIOMETRIC QUALITY AND DSM GENERATION ANALYSIS OF CARTOSAT-1 STEREO IMAGERY

M=8.3

Co-seismic displacement estimation: Improving tsunami early warning systems

M=8.3, 16 September 2015, 22:54:32 UTC) are shown.