Small Local Earthquake Detection Using Low-Cost MEMS Accelerometers: Examples in Northern and Central Italy

This study evaluates the seismicity detection efficiency of a new low-cost triaxial accelerometer prototype based on microelectromechanical systems (MEMS) technology. Networks of MEMS sensors were installed in telecommunication infrastructures to build two small arrays in northern and central Italy. The sensor prototypes recorded major earthquakes as well as nine small seismic events with 2.0<ML<3.0. Where possible, MEMS were compared to the closest high-quality seismic stations belonging to the national accelerometric network. The comparison, in terms of peak ground accelerations and spectral responses, confirms that the signals are in good agreement. The tested inexpensive MEMS sensors were able to detect small local events with epicentral distances as large as 50 km and provided an efficient characterization of the main motion parameters. This confirms that the proposed accelerometer prototypes are promising tools to integrate into traditional networks for local seismicity monitoring.

ACCELEROMETRIC NETWORK AND ELASTIC RESPONSE SPECTRUM FOR GROUND TYPE A IN THE REPUBLIC OF SRPSKA

This paper presents the content of an analysis of available relevant accelerometric data, which aimsat identifying a group of nationally determined parameters in the field of seismological activity thatwas used in the preparation phase of the B&H national annex for Eurocode 8. Seismological dataanalysis related to parameters that are in Eurocode 8 open to national choice, refer to the: soilclassification, horizontal elastic response spectrum and reference ground acceleration, respectivelyseismic hazard map.

The Seismic Network of Zapopan: Evaluating the local seismicity of the western Guadalajara Metropolitan Zone

<p>The Municipality of Zapopan, Jalisco, is located west of the Guadalajara Metropolitan Zone at the intersection of three rift zones: Tepic-Zacoalco, Chapala-Tula, and Colima. The importance of this region lies in the recent population growth that it has experienced in a few years. This growth has been supported by the development in commercial and service activities, and mainly in industry and technology, being ranked as the second-most populous city in Mexico, behind the federal capital.</p><p>The western region of the Guadalajara Metropolitan Zone (GMZ) has numerous fault systems where, historically, there have been significant earthquakes and seismic swarms such as those that occurred in 1685-1687, 1875, 1932, 1995 and 2002, showing similar characteristics. Besides, it is in this region where the Caldera de la Primavera is located, a rhyolitic volcanic caldera that continues presenting seismic and geothermal activity.</p><p>Recently, in the years 2015 and 2016, new seismic swarms occurred and were recorded instrumentally for the first time by the Jalisco Seismic and Accelerometric Network (RESAJ). The two seismic sequences took place in two alignments in the same direction as the Colima rift. These epicenters suggest the existence of two almost parallel normal faults, and that would be forming the Graben of Zapopan. Due to the length of these faults, 16 km for the east fault, and 28 km for the west fault, earthquakes of magnitudes 6.2 - 6.5 could be generated.</p><p>In the framework of the CeMIEGeo P-24 project (SENER-CONACyT), we continue studying the seismicity of this region with the deployment of 25 seismic stations in the vicinity of La Caldera de la Primavera. This study revealed the high seismicity that was taking place in the area of ​​Zapopan, Tesistán Valley, and La Caldera de la Primavera.</p><p>Based on these new studies and the knowledge of the seismic history of the region, a collaboration agreement has been established between the Research Group UDG-CA-276 SisVOc and Civil Protection of the Municipality of Zapopan for the installation of a local seismic network that will allow to define tectonic and structurally the fault systems of the region and mitigate the possible effects of the local seismicity in the population. Since May 2019, three Obsidian 8X seismic stations with Lennartz 1Hz LE3D and Episensor sensors and two accelerometers installed in the city have been operating, constituting the Zapopan Seismic and Accelerometric Network (RESAZ). The RESAZ operates together with the nearest stations of the RESAJ. In this work, we present the first results of the seismicity analysis recorded in Zapopan.</p>

A Candidate Proxy to be used in Intensity-Based Triggering Mechanism for Parametric CAT-Bond Insurance: Istanbul Case Study

We study the suitability of average peak ground acceleration ( PGA) as a ground-motion proxy for parametric catastrophe bond (CAT bond) design. We tie the selection of PGA (as a triggering parameter for CAT bonds) to computational convenience (fast retrieval from the recorded ground motion) and loss correlation (optimum monetary return on the investor side). Our case studies advocate that PGA, as a candidate ground-motion proxy, can be used confidently for parametric CAT bonds, particularly applications associated with dense coverage of seismic networks. It is still a compelling ground-motion proxy even if the seismic network coverage is sparse, provided that the accelerometric stations are deployed in the vicinity of assets that financially represent the most significant portion of the insured building stock. We establish an event-based risk model of the Istanbul city (via Monte Carlo simulations) to depict the rationale behind our proposition and compare its performance with other competing (more sophisticated) proxies in terms of accelerometric network density and spatial distribution as well as the different risk levels used in risk management.

Field Monitoring of Strong Ground Motion in Urban Areas: The Kalochori Accelerometric Network (KAN), Database and Web-GIS Portal

The Kalochori Accelerometric Network (KAN) has been operating since 2014 in the urban area of Kalochori, 7 km west of Thessaloniki in Northern Greece. KAN is composed of seven accelerometric stations: three ground stations installed in distinct urban zones (i.e., residential, industrial, and tanks zone); three stations on top of a selected structure within each urban zone; and one free-field station away from the built environment. The stations are documented with installation and operating features, available characteristics of the housing structures, and geotechnical data. A set of 78 earthquakes that have been recorded by KAN between 16 January 2014 and 31 December 2016 are reported, allowing investigation of local site effects on seismic motion, variation of ground surface motion within different urban environments, and evaluation of dynamic response features of the instrumented structures. KAN stations monographs, processed acceleration recordings, and metadata of the recorded earthquakes are available online through a Web-GIS platform. Indicative example applications are discussed for possible data use in the field of soil and structural dynamics. The DOI linked to the complete set of KAN data is 10.6084/m9.figshare.5044804.

THE ACCELEROMETRIC NETWORK OF THE INDES-MUSA PROJECT IN THE KALOCHORI AREA: CONFIGURATION, DOCUMENTATION AND PRELIMINARY DATA INTERPRETATION

A network of seven accelerometric stations on both ground surface and structures has been recently installed, as part of a multi-sensor network for monitoring seismic motion and ground subsidence in the broader area of Kalochori, west of Thessaloniki in Northern Greece, within the INDES-MUSA project. This network includes ground installations within the urban area, structural stations on top of structures and a freefield station away from the building stock. The documentation of stations is presented including shear wave velocity profiles of the subsoil at each location. A set of thirtynine earthquakes recorded so far by the accelerometric network is reported, followed by data processing procedures performed in the acquired waveforms. Comparisons of the processed earthquake recordings are presented referring to (a) the urbanground and the free-field stations in terms of peak ground acceleration, indicating amplification trends of ground motion, and (b) the structural and the nearby urban ground stations by means of top-to-base ratios in the frequency domain, towards a preliminary identification of the fundamental vibrational characteristics of the instrumented structures. The processed acceleration data are available through the INDES-MUSA Web-GIS portal.

Frecuency-wavenumber analysis of strong ground motion in Mexico City

An analysis of frequency-wavenumber (f-k) spectral power densities of strong ground motion recorded by the Mexico City Accelerometric Network (MCAN) is presented. Time series of a seismic event recorded by the MCAN are analysed. Each recorded motion is assumed to be the insight of a homogeneous random field whose spectral representation reveals an assortment of propagating waves. A kinematic decomposition that separates the waves in longitudinal and transversal displacements was made. These motions are associated to Rayleigh and Love waves, respectively. The analysis on different time windows of the MCAN signals to identify back-propagating waves locally generated as a result of their interactions with shallow geological features was applied. For each component, we estimate the f-k spectral power density, which provide the amplitudes, velocities and directions of propagation of the most significant waves. These values, as functions of frequency, constitute the kinematic spectra of the wave field. Results obtained using this method allow to establish coherent scenarios of the wave field in Mexico City Valley that imply pointing out locally generated surface waves.

Preliminary analysis of the accelerometric recordings of the August 24th, 2016 MW 6.0 Amatrice earthquake

<p>On 24 August 2016, at 1.36:32 GMT, a M_W 6.0 earthquake with epicenter located below the village of Accumoli, struck a wide area among the boundaries of Lazio, Abruzzo, Umbria and Marche regions (Central Italy): the main event caused the collapse of several buildings and about 300 fatalities, mainly in the towns of Amatrice, Arquata del Tronto and Accumoli. The main event was recorded by about 350 sensors, belonging to Italian Accelerometric Network (Rete Accelerometrica Nazionale, RAN), operated by the Department of Civil Protection (DPC), to the Italian Seismic Network (Rete Sismica Nazionale, RSN), managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and to other local networks. All the corrected data are available at the Engineering Strong Motion Database (<a href="http://esm.mi.ingv.it">esm.mi.ingv.it</a>). This paper reports the preliminary results of the analysis of the strong-motion recordings.</p>