scholarly journals Fault-plane solutions from moment-tensor inversion and preliminary Coulomb stress analysis for the Emilia Plain

2012 ◽  
Vol 55 (4) ◽  
Author(s):  
Angela Saraò ◽  
Laura Peruzza
Keyword(s):  
Elastic Stress ◽  
Fault Plane ◽  
Moment Tensor ◽  
Focal Mechanisms ◽  
Structural System ◽  
Fault Plane Solutions ◽  
Stress Changes ◽  
Intermediate Distance ◽  
Complex Structural ◽  
Coulomb Stress Analysis

<p>We investigate the seismicity occurred in the Po area, in the period July 2011-June 1012, by means of moment tensor and we use our set of revised focal mechanisms - computed for M&gt; 3.7 earthquakes - to evaluate Coulomb elastic stress changes in order to detect potential intermediate-distance faults interaction, and the main features of this complex structural system.</p>

scholarly journals A functional tool to explore the reliability of micro-earthquake focal mechanism solution for seismotectonic purposes

2021 ◽  
Author(s):  
Guido Maria Adinolfi ◽  
Raffaella De Matteis ◽  
Rita De Nardis ◽  
Aldo Zollo
Keyword(s):  
Focal Mechanism ◽  
Fault Plane ◽  
Focal Mechanisms ◽  
Seismic Network ◽  
Fault System ◽  
Focal Mechanism Solution ◽  
Fault Plane Solutions ◽  
Stress Regime ◽  
Focal Mechanism Solutions ◽  
Earthquake Focal Mechanism

Abstract. Improving the knowledge of seismogenic faults requires the integration of geological, seismological, and geophysical information. Among several analyses, the definition of earthquake focal mechanisms plays an essential role in providing information about the geometry of individual faults and the stress regime acting in a region. Fault plane solutions can be retrieved by several techniques operating in specific magnitude ranges, both in the time and frequency domain and using different data. For earthquakes of low magnitude, the limited number of available data and their uncertainties can compromise the stability of fault plane solutions. In this work, we propose a useful methodology to evaluate how well a seismic network used to monitor natural and/or induced micro-seismicity estimates focal mechanisms as function of magnitude, location, and kinematics of seismic source and consequently their reliability in defining seismotectonic models. To study the consistency of focal mechanism solutions, we use a Bayesian approach that jointly inverts the P/S long-period spectral-level ratios and the P polarities to infer the fault-plane solutions. We applied this methodology, by computing synthetic data, to the local seismic network operated in the Campania-Lucania Apennines (Southern Italy) to monitor the complex normal fault system activated during the Ms 6.9, 1980 earthquake. We demonstrate that the method we propose can have a double purpose. It can be a valid tool to design or to test the performance of local seismic networks and more generally it can be used to assign an absolute uncertainty to focal mechanism solutions fundamental for seismotectonic studies.

scholarly journals A focal mechanism catalogue of earthquakes that occurred in the southeastern Alps and surrounding areas from 1928–2019

2021 ◽  
Vol 13 (5) ◽  
pp. 2245-2258
Author(s):  
Angela Saraò ◽  
Monica Sugan ◽  
Gianni Bressan ◽  
Gianfranco Renner ◽  
Andrea Restivo
Keyword(s):  
Focal Mechanism ◽  
Moment Tensor ◽  
Active Regions ◽  
Focal Mechanisms ◽  
Seismic Moment Tensor ◽  
Fault Plane Solutions ◽  
First Arrival ◽  
Populated Region ◽  
Surrounding Areas ◽  
Catalogue Of Earthquakes

Abstract. We present a focal mechanism catalogue of earthquakes that occurred in the southeastern Alps and surrounding areas from 1928 to 2019. The area involved in the process of convergence between the Adria microplate and Eurasia is one of the most seismically active regions in the Alpine Belt. The seismicity is minor, with the Ms= 6.5 Friuli earthquake being the strongest event recorded in the area, but the seismic risk is relevant because it is a highly populated region. For this reason, numerous studies have been carried out over time to investigate the stress field and the geodynamic characteristics of the region using focal mechanisms. To provide a comprehensive set of revised information, which is challenging to build quickly because the data are dispersed over many papers, we collected and revised the focal mechanisms that were previously published in the literature. Additionally, depending on the data quality and availability, we computed new focal mechanisms by first arrival polarity inversion or seismic moment tensor. Finally, we merged all the fault plane solutions to obtain a catalogue for a selection of 772 earthquakes with 1.8≤M≤6.5. For each earthquake, we reported all the available focal mechanisms obtained by different authors. We also suggested a preferred solution for users who need information provided expeditiously. The catalogue (https://doi.org/10.5281/zenodo.4660412; Saraò et al., 2021) is given as the Supplement of this paper and will be updated periodically (https://doi.org/10.5281/zenodo.4284970).

scholarly journals Indikasi Sesar Naik di Plampang, Pulau Sumbawa Berdasarkan Analisis Gempa Bumi 13 Juni 2020

EKSPLORIUM ◽  
2021 ◽  
Vol 42 (2) ◽  
pp. 111
Author(s):  
Priyobudi Priyobudi ◽  
Mohamad Ramdhan
Keyword(s):  
Active Fault ◽  
Fault Plane ◽  
Moment Tensor ◽  
Moment Tensor Inversion ◽  
Reverse Fault ◽  
Coulomb Stress Changes ◽  
Stress Changes ◽  
The Moment ◽  
Splay Fault ◽  
Lower Angle

ABSTRAK. Keberadaan sesar aktif dengan pola sesar naik di daerah Plampang berhasil diungkap dari sebaran hiposenter terelokasi, hasil inversi momen tensor, dan pemodelan perubahan tegangan Coulomb. Studi ini juga berhasil mengungkap sumber gempa pada sesar aktif tersebut dengan kedalaman relatif dangkal yang bisa menjadi ancaman di Pulau Sumbawa jika magnitudo maksimumnya rilis di masa yang akan datang. Hasil relokasi hiposenter menunjukkan sebaran episenter berarah barat daya–timur laut. Hal ini didukung juga oleh hasil inversi momen tensor yang menunjukkan bidang sesar berarah barat daya–timur laut (N2240E) dengan dip cukup curam (490). Penampang seismisitas vertikal pada arah dip menunjukkan adanya pola sesar naik yang semakin landai seiring bertambahnya kedalaman. Bidang sesar yang landai menunjukkan struktur decollement pada kedalaman 10–15 km dan berangsur menjadi curam sebagai struktur splay fault pada kedalaman 0–10 km. Hal tersebut konsisten dengan hasil inversi momen tensor yang menunjukkan mekanisme pergerakan sesar naik terjadi pada kedalaman 7 km. Pemodelan perubahan tegangan Coulomb menunjukkan adanya penambahan stress di luar area bidang sesar sehingga memicu terjadinya aftershocks. Sebaran gempa susulan menunjukkan adanya bidang sesar hipotetik dengan panjang 19 km dan lebar 12 km. Sesar sebesar ini berpotensi membangkitkan gempa dengan kekuatan Mw 6,4. Gempa Sumbawa 13 Juni 2020 dengan magnitudo M 5,3 disebabkan oleh sebagian kecil aktivitas dari bidang sesar tersebut.ABSTRACT. The existence of an active fault with a reverse fault mechanism in the Plampang area is successfully delineated from the distribution of the relocated hypocenter, the moment tensor inversion, and the Coulomb stress changes. This study also reveals the source of the earthquake in the active fault with a relatively shallow depth which can be a threat on Sumbawa Island if the maximum magnitude is released in the future. Seismicity from hypocenter relocation shows the distribution of the epicenter with a southwest–northeast direction. It is also supported by the moment tensor inversion result which shows the fault plane trending southwest–northeast (N2240E) with a steep dip (490). The vertical section of seismicity in the dip direction shows that the slope of the plane has a lower angle with increasing depth. The lower angle of a fault plane shows a decollement structure at a depth of 10–15 km and gradually becomes steep as a splay fault structure at a depth of 0–10 km. It is consistent with the result of moment tensor inversion which shows the mechanism of a reverse fault that occurred at a depth of 7 km. The Coulomb stress changes show the stress increasing outside the fault plane area, which triggers aftershocks. The distribution of aftershocks shows a hypothetical fault plane of 19 km long and 12 km wide. A fault of this size has the potential to generate an earthquake with a magnitude maximum of Mw 6.4. The Sumbawa earthquake on June 13, 2020, having M 5.3 was caused by a small part of the activity from the fault.

scholarly journals A functional tool to explore the reliability of micro-earthquake focal mechanism solutions for seismotectonic purposes

Solid Earth ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 65-83
Author(s):  
Guido Maria Adinolfi ◽  
Raffaella De Matteis ◽  
Rita de Nardis ◽  
Aldo Zollo
Keyword(s):  
Focal Mechanism ◽  
Fault Plane ◽  
Normal Fault ◽  
Focal Mechanisms ◽  
Seismic Network ◽  
Fault System ◽  
Fault Plane Solutions ◽  
Stress Regime ◽  
Focal Mechanism Solutions ◽  
Earthquake Focal Mechanism

Abstract. Improving the knowledge of seismogenic faults requires the integration of geological, seismological, and geophysical information. Among several analyses, the definition of earthquake focal mechanisms plays an essential role in providing information about the geometry of individual faults and the stress regime acting in a region. Fault plane solutions can be retrieved by several techniques operating in specific magnitude ranges, both in the time and frequency domain and using different data. For earthquakes of low magnitude, the limited number of available data and their uncertainties can compromise the stability of fault plane solutions. In this work, we propose a useful methodology to evaluate how well a seismic network, used to monitor natural and/or induced micro-seismicity, estimates focal mechanisms as a function of magnitude, location, and kinematics of seismic source and consequently their reliability in defining seismotectonic models. To study the consistency of focal mechanism solutions, we use a Bayesian approach that jointly inverts the P/S long-period spectral-level ratios and the P polarities to infer the fault plane solutions. We applied this methodology, by computing synthetic data, to the local seismic network operating in the Campania–Lucania Apennines (southern Italy) aimed to monitor the complex normal fault system activated during the Ms 6.9, 1980 earthquake. We demonstrate that the method we propose is effective and can be adapted for other case studies with a double purpose. It can be a valid tool to design or to test the performance of local seismic networks, and more generally it can be used to assign an absolute uncertainty to focal mechanism solutions fundamental for seismotectonic studies.

scholarly journals RECENT SEISMIC ACTIVITY IN CENTRAL GREECE REVEALING LOCAL SEISMOTECTONIC PROPERTIES

2017 ◽  
Vol 43 (4) ◽  
pp. 2075
Author(s):  
Ch. K. Karamanos ◽  
V. G. Karakostas ◽  
L. Seeber ◽  
E. E. Papadimitriou ◽  
A.A. Kilias
Keyword(s):  
Fault Zone ◽  
Fault Plane ◽  
Focal Mechanisms ◽  
Normal Faulting ◽  
Seismic Excitations ◽  
Lateral Component ◽  
Fault Plane Solutions ◽  
Central Greece ◽  
Source Characteristics ◽  
The Town

The December 2008, M=5.2 earthquake occurred in the Voiotikos–Kifissos basin near the town of Amfikleia in Central Greece and was followed by an intense sequence with hundreds of earthquakes. Mainshock source characteristics derived from the recordings of the Greek National Seismological Network are consistent with previous known earthquakes as well as with the current nearly N–S extensional regime. The adequate azimuthal coverage and the calculated time residuals at each seismological station ensure high location accuracy, whereas the stations operated close to the seismic excitations constrained 80% of the focal depths between 8 and 12km. Distances from the mainshock epicenter to the 10 closest seismological stations vary from 15 to 75 km. Hypoinverse and HypoDD were used for locations, and FPFIT was used for fault plane solutions of events with an adequate number of clear first arrivals. The hypocenters and focal mechanisms illuminate a ≈10km–long fault zone striking nearly E–W with oblique normal faulting and a small left lateral component. The Voiotikos–Kifissos basin is bordered in the south by two left–stepping en echelon segments known as the Pavliani fault zone and the Parnassos detachment, which strike NW and dip NE. In our preferred interpretation, the Amfikleia mainshock ruptured a previously recognized south–dipping fault antithetic to the basin border faults. This fault may be associated with the left step on the border fault, which would be releasing if that fault had a sinistral component.

Tectonic stress patterns along the Vrancea subcrustal zone from the inversion of focal mechanisms data

2021 ◽  
Author(s):  
Andreea Craiu ◽  
Marius Craiu ◽  
Mariu Mihai ◽  
Elena Manea ◽  
Alexandru Marmureanu
Keyword(s):  
Stress Field ◽  
Large Scale ◽  
Fault Plane ◽  
Numerical Models ◽  
Moment Tensor ◽  
Stress Inversion ◽  
Slab Geometry ◽  
Fault Plane Solutions ◽  
Current Stress ◽  
Stress Patterns

&lt;p&gt;The Vrancea zone is an unique area with both crustal and intermediate-depth seismic activity and constitutes one of the most active seismic area in Europe.&amp;#160; An intense and persistent seismicity is generated between 60 and 180 km depth, within a relic slab sinking nearly vertical in the Earth&amp;#8217;s mantle due to the increasing of the stress state within this volume. At intermediate-depths, large magnitude events are frequent, i.e. four earthquakes with moment magnitudes (Mw) &gt;7 occurred in the last century. An unique slab geometry, likely preserved until the present, causes stress localization due to the slab bending and subsequent stress release resulting in large mantle earthquakes in the region.&lt;/p&gt;&lt;p&gt;In this study, we evaluate the current stress field along the Vrancea subcrustal region by computing the fault plane solutions of 422 seismic events since January 2005. The continuous development of the National Seismic Network allows us to constrain the fault plane solutions and subsequently to evaluate the current stress field.&lt;/p&gt;&lt;p&gt;The main style of faulting for Vrancea subcrustal events presents a predominant reverse one, with two main earthquakes categories: the first one with the nodal planes oriented NE-SW parallel with the Carpathian Arc and the second one with the nodal planes oriented NW-SE perpendicular on the Carpathian Arc. The main axis of the moment tensor may indicate a predominant compressional stress field (Tpl&gt;45&lt;sup&gt;0&lt;/sup&gt; Ppl&lt;45&lt;sup&gt;0&lt;/sup&gt;). Another characteristic of&amp;#160; the Vrancea subcrustal zone is the tendency of the extension axis T to be almost vertical and the compression axis P being almost horizontal.&lt;/p&gt;&lt;p&gt;The results of stress inversion indicate a dominant reverse faulting style, with an average stress regime index of 2.9. Other tectonic regimes were observed in the present dataset as normal and strike-slip but they are retrieved for a restrained number of events.&lt;/p&gt;&lt;p&gt;The stress patterns obtained from formal stress inversion of focal mechanism solutions reveal many features of the current stress field that were not captured by large-scale numerical models.&lt;/p&gt;

scholarly journals The stress field of Vrancea region from fault plane solution (FPS)

2011 ◽  
Vol 11 (10) ◽  
pp. 2817-2820 ◽  
Author(s):  
L. Telesca ◽  
V. Alcaz ◽  
I. Sandu
Keyword(s):  
Stress Field ◽  
Fault Plane ◽  
Moment Tensor ◽  
Field Investigation ◽  
Seismic Region ◽  
Fault Plane Solutions ◽  
Intermediate Depth ◽  
Vrancea Region ◽  
Plane Solution ◽  
Vrancea Seismic Region

Abstract. The fault plane solutions (FPS) of 247 seismic events were used for stress field investigation of the region. The eigenvectors t, p, b, and moment tensor M components for each FPS were defined and computed numerically. The obtained results confirm the hypothesis of subduction-type intermediate depth earthquakes for the Vrancea seismic region and this may be considered the first approximation of the stress field for the whole of the Vrancea (intermediate depth) region.

scholarly journals A focal mechanism catalogue of earthquakes that occurred in the southeastern Alps and surrounding areas from 1928–2019

2021 ◽  
Author(s):  
Angela Saraò ◽  
Monica Sugan ◽  
Gianni Bressan ◽  
Gianfranco Renner ◽  
Andrea Restivo
Keyword(s):  
Focal Mechanism ◽  
Moment Tensor ◽  
Active Regions ◽  
Focal Mechanisms ◽  
Seismic Moment Tensor ◽  
Fault Plane Solutions ◽  
First Arrival ◽  
Populated Region ◽  
Surrounding Areas ◽  
Catalogue Of Earthquakes

Abstract. We present a focal mechanism catalogue of earthquakes that occurred in the southeastern Alps and surrounding areas from 1928 to 2019. The area involved in the process of convergence between the Adria microplate and Eurasia is one of the most seismically active regions in the Alpine Belt. The seismicity is minor, with the Ms =thinsp;6.5 Friuli earthquake being the strongest event recorded in the area, but the seismic hazard is relevant because it is a highly populated region. For this reason, numerous studies have been carried out over time to investigate the stress field and the geodynamic characteristics of the region using focal mechanisms. To provide a comprehensive set of revised information, which is challenging to build quickly because the data is dispersed over many papers, we collected and revised the focal mechanisms that were previously published in the literature. Additionally, depending on the data quality and availability, we computed new focal mechanisms by first arrival polarity inversion or seismic moment tensor. Finally, we merged all the fault plane solutions to obtain a catalogue for a selection of 772 earthquakes with 1.8thinsp;≤thinsp;Mthinsp;≤thinsp;6.5. For each earthquake, we reported all the available focal mechanisms obtained by different authors. However, we also suggested a preferred solution for users who need expeditious information. The catalogue is available at https://doi.org/10.5281/zenodo.4284971 (Saraò et al., 2020).

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