An earthquake swarm affected the Bransfield Strait, Antarctica, a unique rift basin in transition from intra-arc rifting to ocean spreading. The swarm, counting ~85,000 volcano-tectonic earthquakes since August 2020, is located close to the Orca submarine volcano, previously considered inactive. Simultaneously, geodetic data reported up to ~11 cm northwestward displacement over King George Island. We use a broad variety of geophysical data and methods to reveal the complex migration of seismicity, accompanying the intrusion of 0.26–0.56 km3 of magma. Strike-slip earthquakes mark the intrusion at depth, while shallower normal faulting the ~20 km long lateral growth of a dike. Seismicity abruptly decreased after a Mw 6.0 earthquake, suggesting the magmatic dike lost pressure with the slipping of a large fault. A seafloor eruption is likely, but not confirmed by sea surface temperature anomalies. The unrest documents episodic magmatic intrusion in the Bransfield Strait, providing unique insights into active continental rifting.
In this article, we describe the infrastructure developed and managed by the Italian National Institute of Oceanography and Applied Geophysics – OGS for the seismological and geodetic monitoring of northeastern Italy. The infrastructure was constituted in response to the ML 6.4 Friuli destructive earthquake of 1976, with the main mandate of supporting civil protection emergency activities.
The OGS monitoring infrastructure is presently composed of a seismometric and a strong-motion network, complemented by a number of Global Navigation Satellite Systems stations, each delivering observational data in real time, which are collected and processed by the headquarters of the Center for Seismological Research of OGS in Udine. The OGS networks operate in close cooperation with Italian and international networks from neighboring countries, within the framework of the agreements for real-time data exchange, to obtain improved rapid earthquake location and magnitude estimations. Information regarding seismic events is released to the public through a dedicated web portal and, since 2013, through social media.
Aside from the standard monitoring activities (>30,000 events have been recorded since 1976), the OGS has progressively increased the number of services to the public and to the Civil Protection of the Friuli Venezia Giulia and Veneto regions. The high availability of good quality data has resulted in the enhancement of scientific products, including advanced seismological studies of the area, spanning broadly from seismic source characterization to engineering seismology.
In the future, the OGS networks are expected to further contribute to the development of seismological research and monitoring infrastructures of the Central European region.
and it is specifically devoted to the monitoring of the seismicity of north-eastern Italy. Since its inception, the North-East Italy Seismic Network has grown enormously. Currently, it consists of 14 broad-band and 20 short-period seismic stations, all of which are telemetered to and acquired in real time at the OGS-CRS data center in Udine. Data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of 94 seismic stations acquired in real time, which confirms that the OGS is the reference institute for seismic monitoring of north-eastern Italy. Since 2002, CRS has been using the Antelope software suite as the main tool for collecting, analyzing, archiving and exchanging seismic data. SeisComP is also used as a real-time data exchange server tool. A customized webaccessible server is used to manually relocate earthquakes, and automatic procedures have been set-up for moment-tensor determination, shaking-map computation, web publishing of earthquake parametric data, waveform drumplots, state-of-health parameters, and quality checks of the station by spectra analysis. Scripts for email/SMS/fax alerting to public institutions have also been customized. Recently, a real-time seismology website was designed and set-up (http://rts.crs.inogs.it/).
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