8 research outputs found
A large-N passive seismological experiment to unravel the structure and activity of the transcrustal magma system of the Eifel Volcanic Field 
No full text<p align="justify">The Quaternary east (EEVF) and west Eifel volcanic fields consist of hundreds of distributed scoria cone and explosive maar-diatreme volcanoes fed from reservoirs in the upper mantle and lower crust. Uplifting of the larger EVF region of up to 2 mm/yr is resolved today with modern GNSS and InSAR processing, and <span lang="en-US">the distribution of </span>deformation rates correlate with seismic anomalies and topography at Moho level. The EEVF developed additionally explosive volcanic centres, with a VEI 6 Plinean eruption at the Laacher See <span lang="en-US">volcano </span>(LSV) only 13,000 years ago. The LSV is the second youngest silicic-carbonatitic magma system in the world, with CO2-rich melt erupting from a long-lived (>30.000 years) zoned silicic reservoir at a depth of 5-6 km. The phonolitic centres are today characterised by high CO2 fluxes, fossil CO2-driven diatremes and short-term short wavelength uplift and subsidence. Deep low-frequency earthquakes have been observed beneath the LSV since 2013, suggesting a channel-like connection between the upper mantle and the suspected LSV reservoir, through which magmatic volatiles and possibly fresh melts could migrate upwards.</p>
&lt;p align=&quot;justify&quot;&gt;&lt;span lang=&quot;de-DE&quot;&gt;As a uniquely accessible site in central Europe, &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;the &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;Eifel is&lt;/span&gt; &lt;span lang=&quot;de-DE&quot;&gt;a prime location to study &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;the &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;transcrustal &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;magma &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;system &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;of &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;intraplate &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;distributed volcanic fields &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;and their appearance in seismological and geodetic data.&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt; Therefo&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;r&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;e, in September&lt;/span&gt; &lt;span lang=&quot;de-DE&quot;&gt;2022 we started a &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;large-scale &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;field &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;experiment with more than 350 &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;temporary seismological &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;stations (Eifel Large-N) &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;complementing the permanent seismic networks, a 100 km long &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;dark fibre &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;DAS &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;campaign&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt; for a period of three months, and &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;further &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;densif&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;i&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;ed the network of continuous GNSS &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;and multiparameter &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;stations &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;at the LSV&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;. W&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;e report on &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;pre-studies to design the &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;Large-N experiment, &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;the logistical &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;and technical &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;approach to handle the network and data, and &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;show first examples for selected earthquakes, &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;local noise conditions&lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt; and &lt;/span&gt;&lt;span lang=&quot;en-US&quot;&gt;ambient &lt;/span&gt;&lt;span lang=&quot;de-DE&quot;&gt;noise correlations.&lt;/span&gt;&lt;/p&gt;</jats:p
Pushing the limits of CMT inversion with large seismic networks: Challenges and results for small to moderate earthquakes in the Alps
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&lt;p&gt;The AlpArray seismic network (AASN) was operated from 2016 to 2019 by a European initiative aiming for new insights into the orogenesis of the Alps as well as into past and recent geodynamic and tectonic processes. The network included more than 620 temporary and permanent broadband stations with a spacing of 50 - 60 km. It was accompanied by the even denser Swath-D seismic network in the Eastern Alps (~150 stations with 15 km spacing). While the extensive network provides an excellent station coverage for seismicity studies, the large number of stations (up to 100) poses new challenges to MT inversions. Automated quality control and the choice of appropriate configurations becomes crucial for the inversion process. Weak to moderate magnitude events and the complex heterogeneous tectonic setting in the Alps force us to push the limits of full waveform moment tensor inversions.&lt;/p&gt;&lt;p&gt;We develop semi-automatic, adaptive approaches for a standardized quality assessment of large seismic networks and for the selection of appropriate waveform fitting targets and frequency ranges. The earthquake source optimization framework &amp;#8216;Grond&amp;#8217; uses a Bayesian bootstrap-based probabilistic inversion scheme with flexible integration of different waveform attributes in time and frequency domain to provide full or deviatoric moment tensor solutions including uncertainties. The entire workflow from station quality control to moment tensor inversion can handle more than 100 stations simultaneously. The large number of stations allows to study the influence of azimuthal gaps. Further, we are able to compare the inversion results of various methods and configurations in time- and frequency domain using different frequency ranges and epicentral distances. We inverted approximately 100 full moment tensor solutions for events down to Mw 3.1 occurring within the operating time of the AASN. For this magnitude range a combination of frequency-domain spectra and time-domain waveform fitting of surface waves (Z, R and T component, 0.02-0.07 Hz) provides most stable results. In case of distorted absolute amplitudes a combination of frequency spectra and maximum cross-correlation fitting proved to be useful. We find that for smaller events (Mw &lt; 3.0) surface waves are not observed and higher frequency body waves are strongly influenced by complex heterogeneities along the travel path. To extend the source analysis to even weaker events the standard MT inversion approach is combined with network similarity cluster analyses, enabling the association of weaker events to larger ones and therefore the reconstruction of the geometry of active faults.&lt;/p&gt;
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P-wave scattering and the distribution of heterogeneity around Etna volcano
No full text<p>Volcanoes and fault zones are areas of increased heterogeneity in the Earth crust that leads to strong scattering of seismic waves. For the understanding of the volcanic structure and the role of attenuation and scattering processes it is important to investigate the distribution of heterogeneity. We used the signals of air-gun shots to investigate the distribution of heterogeneity around Mount Etna. We devise a new methodology that is based on the coda energy ratio which we define as the ratio between the energy of the direct P-wave and the energy in a later coda window. This is based on the basic assumption that scattering caused by heterogeneity removes energy from the direct P-waves. We show that measurements of the energy ratio are stable with respect to changes of the details of the time windows definitions. As an independent proxy of the scattering strength along the ray path we measure the peak delay time of the direct P-wave. The peak delay time is well correlated with the coda energy ratio. We project the observation in the directions of the incident rays at the stations. Most notably is an area with increased wave scattering in the volcano and east of it. The strong heterogeneity found supports earlier observations and confirms the possibility to use P-wave sources for the determination of scattering properties. We interpret the extension of the highly heterogeneous zone towards the east as a potential signature <span>of inelastic deformation processes</span> induced by the eastward sliding of flank of the volcano.</p></jats:p
Regional centroid MT inversion of small to moderate earthquakes in the Alps using the dense AlpArray seismic network: challenges and seismotectonic insights
No full textAbstract. The Alpine mountains in central Europe are characterized by a heterogeneous crust accumulating different tectonic units and blocks in close proximity to sedimentary foreland basins. Centroid moment tensor inversion provides insight into the faulting mechanisms of earthquakes and related tectonic processes, but is significantly aggravated in such an environment. Thanks to the dense AlpArray seismic network and our flexible bootstrap-based inversion tool Grond we are able to test different set-ups with respect to the uncertainties of the obtained moment tensors and centroid locations. We evaluate the influence of frequency bands, azimuthal gaps, input data types and distance ranges and study the occurrence and reliability of non-DC components. We infer that for most earthquakes (Mw ≥ 3.3) a combination of time domain full waveforms and frequency domain amplitude spectra in a frequency band of 0.02–0.07 Hz is suitable. Relying on the results of our methodological tests, we perform deviatoric MT inversions for events with Mw > 3.0. We present here 75 solutions and analyse our results in the seismo-tectonic context of historic earthquakes, seismic activity of the last three decades and GNSS deformation data. We study regions of high seismic activity, namely the western Alps, the region around Lake Garda, the SE Alps, besides clusters further from the study region, in the northern Dinarides and the Apennines. Seismicity is particularly low in the eastern Alps and in parts of the central Alps. We apply a clustering algorithm to focal mechanisms, considering additional focal mechanisms from existing catalogs. Related to the NS compressional regime, E-W to ENE-WSW striking thrust faulting is mainly observed in the Friuli area in the SE Alps. Strike-slip faulting with a similarly oriented pressure axis is observed along the northern margin of the central Alps and in the northern Dinarides. NW-SE striking normal faulting is observed in the NW Alps showing a similar strike direction as normal faulting earthquakes in the Apennines. Both, our centroid depths as well as hypocentral depths in existing catalogs indicate that Alpine seismicity is predominantly very shallow; about 80 % of the studied events have depths shallower than 10 km.
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Supplementary material to &quot;Regional centroid MT inversion of small to moderate earthquakes in the Alps using the dense AlpArray seismic network: challenges and seismotectonic insights&quot;
No full textRegional centroid moment tensor inversion of small to moderate earthquakes in the Alps using the dense AlpArray seismic network: challenges and seismotectonic insights
No full textAbstract. The Alpine mountains in central Europe are characterized by a heterogeneous crust accumulating different tectonic units and blocks in close proximity to sedimentary foreland basins. Centroid moment tensor inversion provides insight into the faulting mechanisms of earthquakes and related tectonic processes but is significantly aggravated in such an environment. Thanks to the dense AlpArray seismic network and our flexible bootstrap-based inversion tool Grond, we are able to test different setups with respect to the uncertainties of the obtained moment tensors and centroid locations. We evaluate the influence of frequency bands, azimuthal gaps, input data types, and distance ranges and study the occurrence and reliability of non-double-couple (DC) components. We infer that for most earthquakes (Mw≥3.3) a combination of time domain full waveforms and frequency domain amplitude spectra in a frequency band of 0.02–0.07 Hz is suitable. Relying on the results of our methodological tests, we perform deviatoric moment tensor (MT) inversions for events with Mw>3.0. Here, we present 75 solutions for earthquakes between January 2016 and December 2019 and analyze our results in the seismotectonic context of historical earthquakes, seismic activity of the last 3 decades, and GNSS deformation data. We study regions of comparably high seismic activity during the last decades, namely the Western Alps, the region around Lake Garda, and the eastern Southern Alps, as well as clusters further from the study region, i.e., in the northern Dinarides and the Apennines. Seismicity is particularly low in the Eastern Alps and in parts of the Central Alps. We apply a clustering algorithm to focal mechanisms, considering additional mechanisms from existing catalogs. Related to the N–S compressional regime, E–W-to-ENE–WSW-striking thrust faulting is mainly observed in the Friuli area in the eastern Southern Alps. Strike-slip faulting with a similarly oriented pressure axis is observed along the northern margin of the Central Alps and in the northern Dinarides. NW–SE-striking normal faulting is observed in the NW Alps, showing a similar strike direction to normal faulting earthquakes in the Apennines. Both our centroid depths and hypocentral depths in existing catalogs indicate that Alpine seismicity is predominantly very shallow; about 80 % of the studied events have depths shallower than 10 km.</jats:p
The TOMO-ETNA experiment: an imaging active campaign at Mt. Etna volcano. Context, main objectives, working-plans and involved research projects
No full text<p>The TOMO-ETNA experiment was devised to image of the crust underlying the volcanic edifice and, possibly, its plumbing system by using passive and active refraction/reflection seismic methods. This experiment included activities both on-land and offshore with the main objective of obtaining a new high-resolution seismic tomography to improve the knowledge of the crustal structures existing beneath the Etna volcano and northeast Sicily up to Aeolian Islands. The TOMO ETNA experiment was divided in two phases. The first phase started on June 15, 2014 and finalized on July 24, 2014, with the withdrawal of two removable seismic networks (a Short Period Network and a Broadband network composed by 80 and 20 stations respectively) deployed at Etna volcano and surrounding areas. During this first phase the oceanographic research vessel “Sarmiento de Gamboa” and the hydro-oceanographic vessel “Galatea” performed the offshore activities, which includes the deployment of ocean bottom seismometers (OBS), air-gun shooting for Wide Angle Seismic refraction (WAS), Multi-Channel Seismic (MCS) reflection surveys, magnetic surveys and ROV (Remotely Operated Vehicle) dives. This phase finished with the recovery of the short period seismic network. In the second phase the Broadband seismic network remained operative until October 28, 2014, and the R/V “Aegaeo” performed additional MCS surveys during November 19-27, 2014. Overall, the information deriving from TOMO-ETNA experiment could provide the answer to many uncertainties that have arisen while exploiting the large amount of data provided by the cutting-edge monitoring systems of Etna volcano and seismogenic area of eastern Sicily.</p></jats:p
Correction to: Clinical Outcomes of Ambulatory Endovascular Treatment Using 4-French and 6-French Femoral Access Strategies: The Bio4amb Multicentre Trial
No full textThe original version of this paper did not contain a list of Bio4amb investigators.</jats:p
