A First National Seismic Network for the Maltese Islands—The Malta Seismic Network

2021 ◽  
Author(s):  
Pauline Galea ◽  
Matthew R. Agius ◽  
George Bozionelos ◽  
Sebastiano D’Amico ◽  
Daniela Farrugia
Keyword(s):  
Site Response ◽  
Anthropogenic Activities ◽  
Active Faults ◽  
Seismic Monitoring ◽  
Seismic Network ◽  
Time Data ◽  
African Plate ◽  
Small Magnitude ◽  
Maltese Islands ◽  
Sicily Channel

Abstract The Sicily Channel, situated on the leading edge of the African plate as it collides with Europe, presents a range of interesting and complex tectonic processes that have developed in response to various regional stress fields. The characterization and interpretation of the seismic activity, however, still presents a challenge. The Maltese islands, lying approximately 100 km to the south of Sicily, are known to have been affected by a number of earthquakes in the Channel, with some of these events estimated to be very close to the islands. Yet, in the absence of nearby seismic instruments, an accurate evaluation and mapping of small magnitude seismicity, and, hence, the identification of unmapped active faults in the region, remains a challenge. This situation is being partially addressed through the deployment of more seismic stations on the Maltese archipelago. The Malta Seismic Network (MSN; International Federation of Digital Seismograph Networks code ML, see Data and Resources), managed by the Seismic Monitoring and Research Group, within the Department of Geosciences, University of Malta, currently comprises eight broadband, three-component stations covering an area of, approximately, 315  km2. Continuous seismic monitoring is possible following upgrades to real-time data transmission and automated epicenter location, coupled with a virtual seismic network established through SeisComP3, and focused mainly on the Mediterranean region. Such a dense national network, besides improving epicentral location in the Sicily Channel, will provide valuable information on microearthquake activity known to occur in close proximity to the islands, which has been very difficult to study in the past. It will also provide opportunities to study shallow crustal structure, site response on different geological substrates, microseismic noise propagation, and effects of anthropogenic activities. Here, we give a technical description of the MSN and an appraisal of its potential.

The national seismic network for the Maltese islands: Update 2021

2021 ◽  
Author(s):  
Pauline Galea ◽  
Matthew Agius ◽  
George Bozionelos ◽  
Sebastiano D'Amico ◽  
Daniela Farrugia
Keyword(s):  
Real Time ◽  
Site Response ◽  
Seismic Monitoring ◽  
Seismic Network ◽  
Local Network ◽  
Time Data ◽  
African Plate ◽  
Seismic Stations ◽  
Maltese Islands ◽  
Sicily Channel

<p>The Maltese islands are a small country 15 km wide by 30 km long located about 100 km south of Sicily, Italy. Since 2015 Malta has set up a national seismic network. The primary aim of this network is to monitor in real-time and to locate more accurately the seismicity close to the islands and the seismicity in the Sicily Channel, offshore between Sicily, Tunisia and Libya. This Channel presents a range of interesting and complex tectonic processes that have developed in response to various regional stress fields mainly as a result of the collision between the African plate with Europe. The Maltese islands are known to have been affected by a number of earthquakes originating in the Channel, with some of these events estimated to be very close to the islands.</p><p>The seismotectonic characteristics of the Sicily channel, particularly south of the Maltese islands, is not well understood. This situation is being partially addressed through an increase in the number of seismic stations on the Maltese archipelago. The Malta Seismic Network (FDSN code ML), managed by the Seismic Monitoring and Research Group, within the Department of Geosciences, University of Malta, currently comprises 8 broadband, 3-component stations over an area slightly exceeding 300 km<sup>2</sup>. We present a technical description of the MSN including quality control tests such as spectral analysis (Power Spectral Density and HVSR), station orientations and timings as well as examples of local and regional earthquakes recorded on the network. We describe the upgrades to real-time data transmission and archiving, and automated epicentre location for continuous seismic monitoring using the local network amalgamated with a virtual seismic network to monitor the seismicity in the extended Mediterranean region. Such a dense national network, besides improving epicentral location in the Sicily Channel, is providing valuable information on microearthquake activity known to occur in close proximity to the islands, which has been very difficult to study in the past. It also provides an important tool for analysing site response and site amplification related to underlying geology, which constitutes a major component of seismic hazard analysis on the islands. Furthermore, the increase in seismic stations to the seismic monitoring system provides more robust earthquake estimates for the tsunami monitoring/simulation system.</p><p>Funding for stations was provided by Interreg Italia-Malta projects (SIMIT and SIMIT-THARSY, Codes B1-2.19/11 and C1-3.2-57) and by Transport Malta.</p>

scholarly journals Global positioning system resurvey of Southern California Seismic Network stations

1995 ◽  
Vol 85 (1) ◽  
pp. 361-374
Author(s):  
Jennifer S. Haase ◽  
Egill Hauksson ◽  
Hiroo Kanamori ◽  
Jim Mori
Keyword(s):  
Global Positioning System ◽  
Southern California ◽  
Seismic Station ◽  
Seismic Network ◽  
Positioning System ◽  
Dual Frequency ◽  
Time Data ◽  
Phase Measurements ◽  
Station Coordinates ◽  
Global Positioning

Abstract Systematic errors in travel-time data from local earthquakes can sometimes be traced to inaccuracies in the published seismic station coordinates. This prompted a resurvey of the stations of the Caltech/USGS Southern California Seismic Network (SCSN) using the Global Positioning System (GPS). We surveyed 241 stations of the SCSN using Trimble and Ashtech dual-frequency GPS receivers and calculated positions accurate to 3 m using differential positioning from carrier phase measurements. Twelve percent of the stations that were surveyed were found to be mislocated by more than 500 m. Stations of the TERRAscope and USC networks were also surveyed, as well as a network of portable seismic stations deployed shortly after the 1992 Joshua Tree and Landers earthquakes. The new coordinates and the offsets from the old coordinates are given below. The new coordinates are being used in SCSN locations as of 1 January 1994.

Repeatable Source, Path, and Site Effects from the 2019 M 7.1 Ridgecrest Earthquake Sequence

2020 ◽  
Vol 110 (4) ◽  
pp. 1530-1548 ◽  
Author(s):  
Grace A. Parker ◽  
Annemarie S. Baltay ◽  
John Rekoske ◽  
Eric M. Thompson
Keyword(s):  
Los Angeles ◽  
Ground Motion ◽  
Site Response ◽  
Ground Motions ◽  
Warning System ◽  
Site Amplification ◽  
Earthquake Sequence ◽  
Ground Acceleration ◽  
Small Magnitude ◽  
Earthquake Early Warning System

ABSTRACT We use a large instrumental dataset from the 2019 Ridgecrest earthquake sequence (Rekoske et al., 2019, 2020) to examine repeatable source-, path-, and site-specific ground motions. A mixed-effects analysis is used to partition total residuals relative to the Boore et al. (2014; hereafter, BSSA14) ground-motion model. We calculate the Arias intensity stress drop for the earthquakes and find strong correlation with our event terms, indicating that they are consistent with source processes. We look for physically meaningful trends in the partitioned residuals and test the ability of BSSA14 to capture the behavior we observe in the data. We find that BSSA14 is a good match to the median observations for M>4. However, we find bias for individual events, especially those with small magnitude and hypocentral depth≥7  km, for which peak ground acceleration is underpredicted by a factor of 2.5. Although the site amplification term captures the median site response when all sites are considered together, it does not capture variations at individual stations across a range of site conditions. We find strong basin amplification in the Los Angeles, Ventura, and San Gabriel basins. We find weak amplification in the San Bernardino basin, which is contrary to simulation-based findings showing a channeling effect from an event with a north–south azimuth. This and an additional set of ground motions from earthquakes southwest of Los Angeles suggest that there is an azimuth-dependent southern California basin response related to the orientation of regional structures when ground motion from waves traveling south–north are compared with those in the east–west direction. These findings exhibit the power of large, spatially dense ground-motion datasets and make clear that nonergodic models are a way to reduce bias and uncertainty in ground-motion estimation for applications like the U.S. Geological Survey National Seismic Hazard Model and the ShakeAlert earthquake early warning System.

scholarly journals Relationship between seismicity and active faults in Thanh Hoa province detected by local seismic network

2021 ◽  
Vol 43 (2) ◽  
pp. 199-219
Author(s):  
Duong T. N. ◽  
Lai Hop Phong ◽  
Pham D. N. ◽  
Chen C. H. ◽  
Dinh V. T.
Keyword(s):  
Seismic Activity ◽  
Active Faults ◽  
Seismic Network ◽  
Local Network ◽  
Ground Acceleration ◽  
Magnetotelluric Data ◽  
Seismogenic Source ◽  
Tectonically Active ◽  
Relationship Of ◽  
The Relationship

Thanh Hoa province belongs to the southwest part of Northwest Vietnam, which is considered a tectonically active region. In the area of Thanh Hoa province, there are three deep-seated tectonic faults, namely Son La-Bim Son, Song Ma, and Sop Cop. As predicted by scientists, these faults are capable of producing credible earthquakes that might be the strongest in the territory of Vietnam. Besides the three main seismogenic sources, in the province, there are other smaller active faults such as Thuong Xuan-Ba Thuoc and Thuong Xuan-Vinh Loc but the relationship of these faults with seismic activity is still rather blurred. This may due to the sparseness of the Vietnamese National Seismic Network which can not record adequately small earthquakes in the area. This paper presents new results of additional monitoring from a local seismic network using 12 Guralp - 6TD broadband seismometers that have been deployed in Thanh Hoa province since November 2009. We found that the Thanh Hoa area is not seismically quiet. The average number of earthquakes recorded by the network has reached 80 - 90 events per year and some of them have magnitude from ML 3.0 to 4.0.By integration of the earthquake epicenters derived from the local network and distribution of active faults, we can detect several earthquakes locating near the three active faults, not only along the main faults but also along its subsidiary faults. We focused on the active faults of Thuong Xuan-Ba Thuoc and Thuong Xuan-Vinh Loc by using the recent results of the gravity, seismic, and magnetotelluric data analyses. Several recorded earthquakes distribute along the two small faults and some of them reach magnitude 3.0 or greater on the ML scale. In this study, the Thuong Xuan-Vinh Loc is recognized as a seismogenic source. To identify seismic hazard potential caused by earthquakes generated from the active faults, segmentation of the Thuong Xuan - Ba Thuoc fault had been done based on geological and geomorphological indications and seismic activity, and then the peak ground acceleration was determined for each fault segment. Besides, a large number of earthquake epicenters do not have a good correlation with a specific fault, especially in the area of Thanh Hoa coastal plain, which is covered by thick layers of Neogene - Quaternary sediment. This shows that there may be hidden active faults in the area which are needed to study further.

scholarly journals OGS improvements in 2012 in running the North-eastern Italy Seismic Network: the Ferrara VBB borehole seismic station

2014 ◽  
Vol 36 ◽  
pp. 61-67
Author(s):  
D. Pesaresi ◽  
M. Romanelli ◽  
C. Barnaba ◽  
P. L. Bragato ◽  
G. Durì
Keyword(s):  
Real Time ◽  
Seismic Station ◽  
Broad Band ◽  
Seismic Monitoring ◽  
Seismic Network ◽  
Research Centre ◽  
Seismic Stations ◽  
The North ◽  
North Eastern ◽  
Borehole Seismic

Abstract. The Centro di Ricerche Sismologiche (CRS, Seismological Research Centre) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude M=6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the North-eastern Italy Seismic Network: it currently consists of 17 very sensitive broad band and 18 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data centre in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of about 100 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of North-eastern Italy. The south-western edge of the OGS seismic network (Fig. 1) stands on the Po alluvial basin: earthquake localization and characterization in this area is affected by the presence of soft alluvial deposits. OGS ha already experience in running a local seismic network in high noise conditions making use of borehole installations in the case of the micro-seismicity monitoring of a local gas storage site for a private company. Following the ML = 5.9 earthquake that struck the Emilia region around Ferrara in Northern Italy on 20 May 2012 at 02:03:53 UTC, a cooperation of Istituto Nazionale di Geofisica e Vulcanologia, OGS, the Comune di Ferrara and the University of Ferrara lead to the reinstallation of a previously existing very broad band (VBB) borehole seismic station in Ferrara. The aim of the OGS intervention was on one hand to extend its real time seismic monitoring capabilities toward South-West, including Ferrara and its surroundings, and on the other hand to evaluate the seismic response at the site. We will describe improvements in running the North-eastern Italy Seismic Network, including details of the Ferrara VBB borehole station configuration and installation, with first results.

scholarly journals An instrumental earthquake catalogue for the offshore Maltese islands region, 1995–2014

2020 ◽  
Vol 63 (Vol 63 (2020)) ◽  
Author(s):  
Matthew Agius ◽  
Pauline Galea ◽  
Daniela Farrugia ◽  
Sebastiano D'Amico
Keyword(s):  
Seismic Data ◽  
Earthquake Catalogue ◽  
Data Recording ◽  
High Concentration ◽  
Regional Networks ◽  
Regional Seismicity ◽  
Maltese Islands ◽  
Single Station ◽  
Sicily Channel ◽  
Formed Part

We present the first earthquake catalogue for Malta using 20 years of broadband seismic data recording. For about two decades Malta had only one station (WDD) which formed part of regional networks. Its location in the eastern part of the Sicily Channel puts the station at the periphery of these networks with the result that weak, off-shore earthquakes that occur between Malta and Libya, are in many cases recorded on WDD only and are undetected or unlisted by the regional networks. We adopt the single-station earthquake location method to process the continuously recorded seismic data of station WDD from 1995 to 2014. We combine our earthquake list with the bulletins of INGV and IRIS to catalogue 550 earthquakes. We statistically quantify the uncertainties of the earthquake epicentres and establish that many earthquake locations differ from INGV/IRIS locations by < 20 km at local epicentral distances from WDD and that earthquake magnitudes determined from single-station are overestimated by 0.2. We find that the Malta and Linosa grabens are seismically active, and a high concentration of seismic activity is located 80–120 km SSE of Malta at around 35◦N latitude. Closer to land, clusters of epicentres are also located, within 40 km to the east and south of Malta. This new earthquake catalogue shows that the regional seismicity is higher than previously observed and that a number of submarine structures in the area are active as part of the ongoing extension in the Sicily Channel.

scholarly journals The first results of the seismic monitoring system of the Solntsevsky open pit coal mine area (on Sakhalin Island)

2021 ◽  
Vol 946 (1) ◽  
pp. 012002
Author(s):  
D V Kostylev ◽  
N V Boginskaya
Keyword(s):  
Real Time ◽  
Monitoring System ◽  
Coal Mine ◽  
Seismic Monitoring ◽  
Sakhalin Island ◽  
Open Pit ◽  
Seismic Events ◽  
Time Data ◽  
Active Coal ◽  
First Results

Abstract In 2021, work began as a part of the implementation of the decision of the protocol of the Sakhalin branch of the Russian Expert Council on earthquake prediction, seismic hazard and risk assessment dated October 6, 2020 on detailed monitoring in the area of active coal mining at the Solntsevsky open pit coal mine (Sakhalin Island). New points of seismic monitoring were installed directly in the area of the open pit coal mine. Integration of real-time data received from the points in real time into a unified seismic monitoring system in the Sakhalin Region was ensured. The results of registration of seismic events of various origins since the commissioning of the stations are presented. A significant increase in the accuracy of the determined epicenters and the possibilities of determining earthquakes and industrial explosions has been noted. The results of the monitoring system for studying the landslide process in the area of the open pit coal mine, as well as the probable factors that caused the landslide, are shown. The developed monitoring system allows for representative registration of seismic events with ML ≥ 0.8 in the immediate vicinity of open pit coal mine, which makes it possible to control blasting operations with increased accuracy, as well as weak and possible induced seismicity formed as a result of a constant technogenic impact on the subsoil.

scholarly journals Microseismic feasibility study: detection of small magnitude events (Ml<0.0) for mapping active faults in the Betic Cordillera (Spain)

2010 ◽  
Vol 52 (2) ◽  
Author(s):  
Martin Häge ◽  
Manfred Joswig
Keyword(s):  
Feasibility Study ◽  
Active Faults ◽  
Field Measurements ◽  
Small Magnitude ◽  
Magnitude Distribution ◽  
Short Period ◽  
Actual Field ◽  
Frequency Magnitude Distribution ◽  
Central Station ◽  
Frequency Magnitude

We present the results of the first application of the newly developed concept «Nanoseismic Monitoring» on active<br />faults in the region close to Murcia, Spain. The aim of this microseismic feasibility study is to test if it is possible<br />to record small magnitude events (ML<0.0) within a short period of time with surface installations and to investigate<br />if these events are related to the regional catalog in terms of amount of events. The seismic monitoring<br />was performed with one small array called the Seismic Navigating System. It consists of one central three component<br />and three one component seismometers arranged tripartitely around the central station. In the measurement<br />period of two nights at two different sites we were able to detect 19 microearthquakes down to ML = -2.6. The results<br />correlate well with the frequency-magnitude distribution of the regional bulletin. This in turn will allow for<br />estimation of monitoring rates before actual field measurements just from bulletin data. Given an activity rate of<br />5 to 10 events per night one may map active fault zones within just a few weeks of field campaign.

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