ARTICLE | doi:10.20944/preprints201704.0081.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: Northern Papua; Subduction; Seismicity
Online: 14 April 2017 (05:55:31 CEST)
Papua is one of part in Indonesia which is the geology research of that place isn’t developed and limited. It causes the seismotectonic of Papua hasn’t been known. WinITDB was used to determine the dip angle plate which was on the north part of Papua. The determination of angle was done through seismicity’s cross section analysis in the area. To show that seismicity, earthquake history data that ever occurred in the area is needed. The result on the seismicity’s cross section of plane A–A’, was confluence by two plates with angle 150° against horizontal on the depth up to ±68 km. On the seismicity’s cross section of plane B–B’ had angle 135° against horizontal on the ±82 km depth. On the plane C–C’ seismicity’s cross section, was confluence of two plate which located between -1,77°S until -4,97°S subducted until 171 km depth on 1,38°N - 4,97°S. It proved that subduction characteristic in the northern Papua which was Australia continent plate subducted to north, followed by collision and the Pacific plate subduction on New Guinea. It is also confirmed by focus mechanism analysis which showed the earthquake activities are controlled by the not really deep active fault.
ARTICLE | doi:10.20944/preprints202012.0046.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: deep; eruption; precursor; seismicity; tectonic; volcano
Online: 2 December 2020 (07:59:11 CET)
An eruption of volcano is related to the past volcanic and tectonic seismicity. Recently, on November 29, 2020, a 1423 m Mount Ile Lewotolok in Lembata Island has erupted. In here, this paper aimed to assess the volcanic and tectonic seismicity as determinant factor and precursor of recent Mt Ile Lewotolok eruption. The assessment shows that Mt Ile Lewotolok volcanic activities were characterized by both tectonic and deep volcanic seismicity. Since 2010, mean tectonic quake magnitudes of M 4.133 (95%CI:M 3.205-5.062) have occurred at mean depth of 13.500 km (95%CI:8.201-18.799 km) within a distance of 3-4 km from the summit. Tectonic quake has occurred frequently in southwest of Ile Lewotolok and this has contributed to the past eruptions in 2012 and 2017. Recent eruption has been influenced by deep volcanic seismicity rather than local tectonic. Based on November 2020 record, mean of deep volcanic seismicity frequency was 2.190 events/day (95%CI:1.136-3.243 events/day km) that has outnumbered (ttest=2.665, P=0.013) the events of local tectonic quakes (mean 0.621 events/day; 95%CI:0.142-1.099events/day). Prior to the eruption there was significant increase of deep volcanic seismicity (P=0.023) while local tectonic quake was not showing an increasing trend (P=0.764). This result confirms that the deep volcanic seismicity frequency is a precursor that may trigger the eruption and deep volcanic seismicity data can be used as indicator of volcanic activities.
ARTICLE | doi:10.20944/preprints202305.1143.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: seismicity; b-value; seismic quiescence; Vrancea intermediate-depth earthquakes
Online: 16 May 2023 (09:43:29 CEST)
(1) Background: The intermediate-depth seismicity in the Vrancea region (Romania) is characterized by localized and persistent earthquake activity that culminates about two or three times in a century with the occurrence of a large event (M 6.5). Here we have revisited some important seismicity characteristics, using earthquake catalog data spanning two different time periods: 2005 – 2013 and 1960 – 2000. (2) Methods: we have determined the b-value of the frequency-magnitude distribution of earthquakes, using a maximum likelihood procedure, and estimated the parameter to quantify anomalous seismicity rate decreases and increases. (3) Results: by using data from the first period, we have confirmed the existence of a decreased b-value in the deepest part of the seismogenic zone; by using data from the second period, we have statistically confirmed the seismic quiescence that preceded the occurrence of the 1977 M7.4 Vrancea earthquake. (4) Conclusions: the decreased b-value has been interpreted either in terms of an increased lithostatic stress with depth or as an indicator of the depth range where the next major Vrancea earthquake may occur. The time variation of the seismicity parameter may reveal anomalous seismic quiescence and increased earthquake rates that may precede the occurrence of large earthquakes.
ARTICLE | doi:10.20944/preprints202203.0361.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: Induced seismicity Monitoring; seismic arrays; sensor network technology; microearthquake detection
Online: 28 March 2022 (11:12:18 CEST)
Seismic monitoring in areas where induced earthquakes could occur is a challenging topic for seismologists due to generally very low signal to noise ratio. Therefore, the seismological com-munity is devoting several efforts to the development of high-quality networks around the areas where fluid injection and storage and geothermal activities take place, also following the national induced seismicity monitoring guidelines. The use of advanced data-mining strategy, such as template matching filters, auto-similarity search and deep-learning approaches is recently further fostering such a monitoring enhancing the seismic catalogues and lowering the magnitude of completeness of these areas. In this framework, we carried out an experiment where a small-aperture seismic array was installed around the gas reservoir of Collalto, in North Italy. The continuous velocimetric data, acquired for 25 days, were analysed through the application of the optimized auto-similarity search technique FAST. The array was conceived as a cost-effective network, aimed at integrating, right above the gas storage site, the permanent high-resolution Collalto Seismic Network. The analysis allowed to detect micro-events down to magnitude Ml=-0.4 within a distance of ~15km from the array. Our results confirmed that the system based on the array installation and the FAST data-analysis might contribute to lower the magnitude of completeness around the site of about 0.7.
ARTICLE | doi:10.20944/preprints201805.0282.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: hydraulic fracturing; hollow cylinder; single fracture; fault activation; induced seismicity
Online: 22 May 2018 (05:04:47 CEST)
Pre-existing fracture and secondary cracks in rock mass are formed by natural power, such as magma condensed to igneous rocks and tectonic movement. The orientation and inclination of these fractures obey certain laws relating to the stress, temperature, minerals, water and so on. Therefore, cracks react differently under the same external loading on the condition of various inclination, fissure apertures, stiffness and joint roughness. To simulate the crack propagation, experiments on hollow cylinder cut by one oblique interface mimicking single fracture accumulated numerous data discovering the failure criterion in accordance with the Mohr-Coulomb criterion. And theory on the Terzaghi’s effective principle take an essential role in controlling the behavior of triggering fault. This paper introduced a series of oblique plane cutting the cylinder regarded as fractures at different inclination to concentrate on how the fracture characteristics effect the stress and strain distribution inside the specimen, especially, the relationship between displacement and water head. The key point of this numerical simulation is coupling the solid phase and the fluid phase, specifically, the mechanic and seepage field. According to the statics, curves referring to deformation and water head could be described as increasing lines. Besides, simulation on coupling solid phase and fluid phase can supply crucial evaluation on activating existing fault, and thus predicting induced seismicity in reservoirs or estimating damage in shale gas exploration.
ARTICLE | doi:10.20944/preprints202308.0209.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: Earth's rotation-related; seismicity; the Mw 7.8 Turkey earthquake; Schuster test; precursor
Online: 3 August 2023 (08:02:26 CEST)
For earthquakes (M4.0) occurring along and arond the East Anatolian fault zone and the the Dead Sea fault zone between January 2002 and December 2022, we analyzed the correlation between the Earth's rotation and the earthquake occurrence before the Mw7.8 Gaziantep,Turkey earthquake occurring on 6 February 2023. We statistically evaluate the Earth's rotationally dependent seismicity. The results were judged by the P-value. There was a clear downward trend in the P-values from early 2020 to late 2022 in the study region. Starting in early 2021, the P-value drops below 0.1%, corresponding significant correlation between the Earth's rotation and the earthquake occurrence . We also calculated the spatial distribution of the P-values and obtained a result showing a low P-value area in the vicinity of the northeastern end of the aftershock zone. Although the stress caused by the Earth's rotation is very weak, when the focal medium is loaded to the critical state to release a large earthquake, the stress due to the Earth's rotation could control the earthauqke occurrence. Therefore, the lower P-values obtained in this study indicates the Earth's rotation-related seismicity prior to the Mw 7.8 Turkey earthquake and could be considered as its precursor.
ARTICLE | doi:10.3390/sci1010002
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: atmospheric evolution; seismicity; low-energy nuclear reactions; carbon pollution; time series analysis
Online: 28 September 2018 (00:00:00 CEST)
The crucial stages in the geochemical evolution of the Earth’s crust, ocean, and atmosphere could be explained by the assumed low-energy nuclear reactions (LENR) that are triggered by seismic activity. LENR result in the fission of medium-weight elements accompanied by neutron emissions, involving Fe and Ni as starting elements, and C, N, O as resultants. Geochemical data and experimental evidences support the LENR hypothesis. A spectral analysis of the period 1955-2013 shows common cycles between interannual changes in atmospheric CO2 growth rate and global seismic-moment release, whereas the trending behavior of the atmospheric CO2 was in response to the anthropogenic emissions. Assuming a correlation between such seismic and atmospheric fluctuations, the latter could be explained by cycles of worldwide seismicity, which would trigger massively LENR in the Earth’s Crust. In this framework, LENR from active faults could be considered as a relevant cause of carbon formation and degassing of freshly-formed CO2 during seismic activity. However, further studies are necessary to validate the present hypothesis which, at the present time, mainly aims to stimulate debate on the models which regulates atmospheric CO2.
ARTICLE | doi:10.20944/preprints202208.0092.v2
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: hydrogeological effects; hydro-geomechanical modelling; Andalusia 1884 Earthquake, pore pressure effects; poroelasticity and seismicity
Online: 25 January 2023 (04:04:50 CET)
The 1884 Andalusia Earthquake, with an estimated Magnitude between 6.2 and 6.7, is one of the most destructive events that shook the Iberian Peninsula, causing around 1200 casualties. Ac-cording to paleoseismology studies and intensity maps, the earthquake source relates to the nor-mal Ventas de Zafarraya Fault (Granada, Spain). Diverse studies registered and later analyzed hydrological effects, such as landslides, rockfalls, soil liquefaction, all-around surge and loss of springs, alterations in the phreatic level, discharge in springs and brooks, and well levels, along with changes in water properties. Further insight into these phenomena found an interplay be-tween hydro-geomechanical processes and crust surface deformations, conditions, and properties. This study focuses on analyzing and simulating the features involved in the major 1884 event and aims at elucidating the mechanisms concerning the mentioned effects. This ex-post analysis builds on the qualitative effects and visible alterations registered by historical studies. It encompasses conceptual geological and kinematic models, and a 2D finite element simulation to account for the processes undergone by the Zafarraya Fault. The study focuses on the variability of hy-dro-geomechanical features and the time evolution of the ground pore-pressure distribution in both the preseismic and coseismic stages, matching some of the shreds of evidence found by field studies. This methodology can be applied to other events registered in the National Catalogues of Earth-quakes to achieve a deeper insight, further knowledge, and a better understanding of past earth-quakes.
ARTICLE | doi:10.20944/preprints202009.0080.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: earthquake; source observations; body wave modeling; seismicity; ionian sea; gnss; machine learning; neural network
Online: 4 September 2020 (04:08:49 CEST)
During the period January 2014 – October 2018, four strong earthquakes occurred in the Ionian Sea, Greece. A rich aftershock sequence followed each event of them. More analytically, according to the manual solutions of National Observatory of Athens, the first event (K1), occurred on 26 January 2014 in Kefallinia Island with magnitude ML = 5.8, which was followed by another in the same region (K2) on 3 February 2014 with magnitude ML = 5.7. The third event occurred on 17 November 2015, ML = 6.0 in Lefkas Island (L1) and the last on 25 October 2018, ML = 6.6 in Zande Island (Z1). The first three of these earthquakes caused moderate structural damages mainly in houses and produced particular unrest to the local population. This work presents first the calculation of the source parameters of the strong events as well as for all earthquakes with magnitude ML > 4.0, using the methodology of the Moment tensor inversion and secondary data from permanent GPS stations were analyzed to confirm the findings from seismological data and to investigate the displacement due to the earthquakes.