The new Algerian Digital Seismic Network (ADSN): towards an earthquake early-warning system

Abstract

Abstract. Seismic monitoring in Algeria has seen great changes since the Boumerdes earthquake of 21 May 2003. Indeed, the installation of a new digital seismic network has resulted in a significant upgrade of the previous analog telemetry network.During the last four years, the number of stations in operation has increased substantially from 25 to 69, and 20 of these are broadband, 2 are very broadband, 47 are short period. 21 are equipped with accelerometers. They are all managed by Antelope software from Kinemetrics (US Cie), and they are all connected in real time and use various modes of transmission (e.g., satellite, internet, mobile phone). The spatial repartition of the stations now cover most of northern Algeria. In addition, 70 GPS stations have recently been added to this seismological network, most of them collocated with the seismological stations.Since the installation of the network, the records of local or distant events have improved significantly. The automatic processing of the data in a few minutes allows alert messages to be distributed to Civil Defense and other national authorities to react promptly to any emergency. The current strategy is to improve the data quality, to increase the density of the network by adding about 50 new stations, to reduce the processing time, and to reduce the time needed to send out an alert message. The result should be greatly improved network performance, which will lead to an effective earlywarning system.

The 2007 Medea Seismic Sequence, North-Central Algeria: Source Parameters, Stress Tensor, and Static Stress Changes

“…(2) The Ben Chicao fault-related fold is a N65°E-striking, asymmetrical anticline with a steep dip (50-90°) along its northern flank and shallow dip (\35°) along its southern flank. The northern flank is bounded by a reverse fault with the same alignment as the axis of the fold, and the fault throw is estimated to be 50-100 m over a length of *5 km (Boudiaf, 1996;Roman, 1975;Yelles-Chaouche et al, 2006).…”

“…3a). The ADSN is composed of eight broadband seismic stations (BBVS-60; Chinese product), two very broadband seismic stations (GCZ-NT 120 s; Chinese product), and 32 short-period digitized seismic stations equipped with seismometers SS1 and L22 (Beldjoudi et al, 2011;Yelles-Chaouche et al, 2013). We analyzed the records of eight broadband and ten short-period stations to locate all the events.…”

The large Algerian earthquakes (267 A.D.-2017)

“…Indeed, since the installation of the Algerian network in 1990 , and although some damage in the period (1991)(1992)(1993)(1994)(1995)(1996)(1997), it was possible to record with accuracy the seismic activity of northern Algeria. This network was improved technically in 1998 by its transformation from the analog mode to the digital mode (Yelles-Chaouche et al, 2013). It permitted to face the moderate Ain Temouchent earthquake of December 22 To understand seismicity of northern Algeria, we also launched fifteen years ago two main projects: the Maradja project (2003)(2004)(2005)(2006)(2007)(2008)(2009) for the study of the active tectonics of the Algerian margin and also the SPIRAL project (2009)(2010)(2011)(2012)(2013)(2014) to understand the crustal structure along the transitional zone between the Ocean and Continent.…”

“…Although, the knowledge of the seismic activity in northern Algeria has improved consequently with the study of the large earthquakes, some important geophysical projects recently implemented led to know more about the Algerian seismicity. Indeed, such projects as the installation of the new digital seismic network (ADSN Network) in 1998 (Yelles-Chaouche et al, 2013), the Maradja project (Yelles-Chaouche et al, 2006a), the Spiral project (Yelles-Chaouche et al, 2010) or the REGAT Atlas GPS network project (Lammali et al, 2015) provide valuable results to understand mechanisms of the Algerian seismicity.…”

REGAT: A permanent GPS network in Algeria, configuration and first results

“…The May 21, 2003, M w 6.8 Boumerdes earthquake (Yelles et al, 2003; Delouis et al, 2004; Yelles et al, 2004) was a motivation for important changes in the seismic monitoring strategy of the CRAAG. A significant upgrade of the analog telemetric network was performed, with the installation of a new digital seismic network (Yelles-Chaouche et al, 2013). Also, the Boumerdes earthquake sparked new efforts to increase deformation monitoring capabilities over the most seismically active part of Algeria through campaign measurements in selected areas and the installation of a cGPS network.…”