scholarly journals Rn and CO<sub>2</sub> geochemistry of soil gas across the active fault zones in the capital area of China

2014 ◽  
Vol 2 (2) ◽  
pp. 1729-1757 ◽  
Author(s):  
X. Han ◽  
Y. Li ◽  
J. Du ◽  
X. Zhou ◽  
C. Xie ◽  
...  
Keyword(s):  
Active Fault ◽  
Emission Rate ◽  
Active Faults ◽  
Soil Gas ◽  
Spatiotemporal Variations ◽  
Gas Emission ◽  
North East ◽  
The North ◽  
Soil Gas Survey ◽  
Soil Gas Sampling

Abstract. The present work is proposed to investigate the spatiotemporal variations of soil gas Rn and CO2 across the active faults in the capital area of China, for the understanding of fault activities and the assessment of seismic hazard. A total of 342 soil gas sampling sites were measured twice in 2011 and 2012 along seven profiles across four faults. The results of soil gas surveys show that in each profile, due to the variation of gas emission rate, the concentrations of Rn and CO2 changed in the vicinity of faults. Spatial distributions of Rn and CO2 in the study areas were different from each other, which was attributed to soil types affecting the existence of Rn and CO2. Compared with 2011 soil gas survey, the increases of Rn and CO2 concentrations in 2012 were related to the enhancement of seismic activities in the capital area of China. Our results indicate that special attention for seismic monitoring should be paid to Xinbaoan-Shacheng Fault and the north east segment of Tangshan Fault in the future.

scholarly journals Rn and CO<sub>2</sub> geochemistry of soil gas across the active fault zones in the capital area of China

2014 ◽  
Vol 14 (10) ◽  
pp. 2803-2815 ◽  
Author(s):  
X. Han ◽  
Y. Li ◽  
J. Du ◽  
X. Zhou ◽  
C. Xie ◽  
...  
Keyword(s):  
Active Fault ◽  
Emission Rate ◽  
Active Faults ◽  
Fault Zones ◽  
Average Concentration ◽  
Soil Gas ◽  
Spatiotemporal Variations ◽  
Gas Emission ◽  
Gas Sampling ◽  
Soil Gas Sampling

Abstract. The present work is proposed to investigate the spatiotemporal variations in soil gas Rn and CO2 across the active faults in the capital area of China in order to understand fault activities and assess seismic hazard. A total of 342 soil gas sampling sites were measured twice in 2011 and 2012 along seven profiles and across four faults. The results of soil gas surveys show that, in each profile, due to the variation in gas emission rate, the concentrations of Rn and CO2 changed in the vicinity of faults. Spatial distributions of Rn and CO2 in the study areas were different from each other, which was attributed to soil types affecting the existence of Rn and CO2. Compared with the measurement result of 2011, the increasing amplitude of average concentration value of Rn and CO2 in profiles in 2012 ranged from 30.2 to 123.4% and 66.3 to 131.7%, respectively, which were coincident with the enhancement of seismic activities in the capital area of China. Our results indicate that special attention with regard to seismic monitoring should be paid to the Xinbaoan–Shacheng Fault and the northeastern segment of the Tangshan Fault in the future.

scholarly journals Soil gas geochemical behaviour across buried and exposed faults during the 24 august 2016 central Italy earthquake

2016 ◽  
Vol 59 ◽  
Author(s):  
Giancarlo Ciotoli ◽  
Alessandra Sciarra ◽  
Livio Ruggiero ◽  
Aldo Annunziatellis ◽  
Sabina Bigi
Keyword(s):  
Active Fault ◽  
Central Italy ◽  
Soil Gas ◽  
Seismic Sequence ◽  
Spatial Behaviour ◽  
Fault Rupture ◽  
Central Italy Earthquake ◽  
Geochemical Behaviour ◽  
Buried Fault ◽  
Soil Gas Survey

<p>Following the earthquake (M<sub>L</sub>=6.0) of 24 August 2016 that affected large part of the central Apennine between the municipalities of Norcia (PG) and Amatrice (RI) (central Italy), two soil gas profiles (i.e., <sup>222</sup>Rn, <sup>220</sup>Rn, CO<sub>2</sub> and CO<sub>2</sub> flux) were carried out across buried and exposed coseismic fault rupture of the Mt. Vettore fault during the seismic sequence. The objective of the survey was to explore the mechanisms of migration and the spatial behaviour of different gas species near still-degassing active fault. Results provide higher gas and CO<sub>2</sub> flux values (about twice for <sup>222</sup>Rn and CO<sub>2</sub> flux) in correspondence of the buried sector of the fault than those measured across the exposed coseismic rupture. Anomalous peaks due to advective migration are clearly visible on both side of the buried fault (profile 1), whereas the lower soil gas concentrations measured across the exposed coseimic rupture (profile 2) are mainly caused by shallow and still acting diffusive degassing associated to faulting during the seismic sequence. These results confirm the usefulness of the soil gas survey to spatially recognise the shallow geometry of hidden faults, and to discriminate the geochemical migration mechanisms occurring at buried and exposed faults related to seismic activity.</p>

Monitoring of diffuse CO2 degassing at NERZ, NWRZ and NSRZ volcanic systems of Tenerife, Canary Islands

2021 ◽  
Author(s):  
Fátima Rodríguez ◽  
Eleazar Padrón ◽  
Gladys Melián ◽  
María Asensio-Ramos ◽  
Mar Alonso ◽  
...  
Keyword(s):  
Rift Zone ◽  
Emission Rate ◽  
Interpolation Method ◽  
Sampling Site ◽  
Sequential Gaussian Simulation ◽  
Rift System ◽  
Volcanic Complex ◽  
North East ◽  
The North ◽  
Volcanic Seismicity

&lt;p&gt;One of the main volcano-structural and geomorphological feature in Tenerife (2,034 km&lt;sup&gt;2&lt;/sup&gt;) is the triple rift system, formed by aligned of hundreds of monogenetic eruptive products of shield basaltic volcanism. At the intersection of this triple rift system rises the Teide-Pico Viejo volcanic complex. These volcanic rifts are considered as active volcanic edifices. The North East volcanic Rift Zone (NERZ, 210 km&lt;sup&gt;2&lt;/sup&gt;) form a main NE-SW structure. The North West volcanic Rift Zone (NWRZ, 72 km&lt;sup&gt;2&lt;/sup&gt;) is oriented in NW-SE direction and the North South volcanic Rift Zone (NSRZ, 325 km&lt;sup&gt;2&lt;/sup&gt;) comprises a more scattered area on the south of these monogenetic cones. The most recent eruptive activity of Tenerife has taken place in these rift systems. NERZ host the fissural eruption of Arafo-Fasnia-Siete Fuentes (1704-1705). NWRZ host two historical eruptions: Arenas Negras in 1706 and Chinyero in 1909. Recently the eruption of Boca Cangrejo (1492) has been added to the historical register through &lt;sup&gt;14&lt;/sup&gt;C dating. NSRZ does not host historical volcanism, although it is recent, up to 10,000 years old.&lt;/p&gt;&lt;p&gt;In order to provide a multidisciplinary approach to monitor potential volcanic activity changes at the NERZ, NWRZ and NSRZ, diffuse CO&lt;sub&gt;2&lt;/sub&gt; emission surveys have been undertaken since 2000, in general in a yearly basis, but with a higher frequency when seismic swarms have occurred in and around NWRZ volcano. Each study area for NERZ, NWRZ and NSRZ comprises hundreds of sampling sites homogenously distributed. Soil CO&lt;sub&gt;2&lt;/sub&gt; efflux measurements at each sampling site were conducted at the surface environment by means of a portable non-dispersive infrared spectrophotometer (NDIR) LICOR Li820 following the accumulation chamber method. To quantify the CO&lt;sub&gt;2&lt;/sub&gt; emission rate from the NERZ, NWRZ and NSRZ a sequential Gaussian simulation (sGs) was used as interpolation method.&lt;/p&gt;&lt;p&gt;The diffuse CO&lt;sub&gt;2&lt;/sub&gt; emission rate for the NERZ ranged from 532 up to 2823 t d&lt;sup&gt;-1 &lt;/sup&gt;between 2001 and 2020, with the highest value measured in 2020. In the case of NWRZ, the diffuse CO&lt;sub&gt;2&lt;/sub&gt; emission rate ranged from 52 up to 867 t d&lt;sup&gt;-1 &lt;/sup&gt;between 2000 and 2020, with the highest value measured in one of the surveys of 2005. Finally, and for NSRZ, the diffuse CO&lt;sub&gt;2&lt;/sub&gt; emission rate ranged from 78 up to 819 t d&lt;sup&gt;-1 &lt;/sup&gt;between 2002 and 2020, with the highest value measured in 2019. The temporal evolution of diffuse CO&lt;sub&gt;2&lt;/sub&gt; emission at the NERZ, NWRZ and NSRZ shows a nice and clear relationship with the volcanic seismicity in and around Tenerife Island, which started to take place from the end of 2016. The good temporal correlation between the volcanic seismicity and the increase trend observed in the time series of diffuse CO&lt;sub&gt;2&lt;/sub&gt; emission rates at NERZ, NWRZ and NSRZ is also coincident with the observed increase of diffuse CO&lt;sub&gt;2&lt;/sub&gt; emission rate at the summit crater of Teide. This work demonstrates the importance of performing soil CO&lt;sub&gt;2&lt;/sub&gt; efflux surveys at active rift systems in volcanic oceanic islands as an effective geochemical monitoring tool.&lt;/p&gt;

scholarly journals Intra-Crustal Seismicity Triggering in Shillong Massif – An Appraisal on Recent Seismicity

2021 ◽  
Vol 16 (1) ◽  
pp. 221-226
Author(s):  
Himanta Borgohain
Keyword(s):  
Active Faults ◽  
Temporal Distribution ◽  
Seismogenic Zone ◽  
Shillong Plateau ◽  
Seismicity Pattern ◽  
North East India ◽  
North East ◽  
The North ◽  
Seismicity Monitoring ◽  
Mountain Belts

Shillong plateau in the North East India resembles a kind of inselberg, confined in between the great Hilamalayan mountain belts in the north and the Arakan-Yoma towards east. The study area is governed by a system of complex seismotectonic features responsible for the intense seismicity in the region, significantly the devastation aftermath the 1897 great Assam Earthquake (Ms~8.7). Spatio-temporal distribution of seismicity triggering inside the plateau from 1966 to 2013 suggests distinctly variable depth-ranges of seismicity zones within the crust. The depth section counterparts of the seismicity monitoring within Shillong plateau and its periphery infers the bottom of the seismogenic zone to lie at ~40km depth with an average depth of earthquake occurrence at 22.31km; besides, the study also dictates the dominant earthquake magnitude as ≤4.99Mw, wherein most of the earthquakes are confined within magnitude 3-5 Mw with an average magnitude 3.42 MW. The study reveals intense seismic activity in the central and western part of Shillong plateau owing to the conjecture of a number of active faults. The present study incorporates both qualitative as well as quantitative approach while understanding the types of recent seismicity pattern in the Shillong massif.

scholarly journals Mapping and evaluating kinematics and stress/strain field at active faults and fissures: a comparison between field and drone data at NE Rift, Mt Etna (Italy)

2021 ◽  
Author(s):  
Alessandro Tibaldi ◽  
Noemi Corti ◽  
Emanuela De Beni ◽  
Fabio Luca Bonali ◽  
Susanna Falsaperla ◽  
...  
Keyword(s):  
Stress Field ◽  
Best Practice ◽  
Ground Deformation ◽  
Active Faults ◽  
Normal Faults ◽  
Extension Rate ◽  
North East ◽  
The North ◽  
Mt Etna ◽  
Dyke Injection

Abstract. We collected drone data to quantify the kinematics at extensional fractures and normal faults, integrated this information with seismological data to reconstruct the stress field, and critically compared the results with previous fieldwork to assess the best practice. As key site, we analysed a sector of the North-East Rift of Mt Etna, an area affected by continuous ground deformation linked to gravity sliding of the volcano's eastern flank and dyke injection. The studied sector is characterized also by the existence of eruptive craters and fissures and lava flows. This work shows that this rift segment is affected by a series of NE-striking, parallel extensional fractures characterized by an opening mode along an average N105.7° vector. Normal faults strike parallel to the extensional fractures, although they tend to bend slightly when crossing topographic highs corresponding to pyroclastic cones. The extensional strain obtained by cumulating the net offset at extensional fractures with the fault heave gives a stretching ratio of 1.003 in the northeastern part of the study area and 1.005 in the southwestern part. Given a maximum age of 1614 yr AD for the offset lavas, we obtained an extension rate of 1.9 cm/yr for the last 406 yr. The stress field is characterised by a σHmin trending NW-SE. Results indicate that Structure-from-Motion photogrammetry applied to drone surveys allows to collect large amounts of data with a resolution of 2–3 cm, a detail comparable to field surveys. In the same amount of time, drone survey can allow to collect more data than classical fieldwork, especially in logistically difficult rough terrains.

scholarly journals The pattern and magnitude of rotational piezomagnetic anomalies along the dip-slip Mosha fault, Northern Tehran, Iran

2008 ◽  
Vol 8 (6) ◽  
pp. 1293-1297
Author(s):  
M. Mokhtari ◽  
S. Kiarasi
Keyword(s):  
Analytical Solution ◽  
Computer Program ◽  
Active Fault ◽  
Active Faults ◽  
The Other ◽  
Magnetic Data ◽  
Northern Iran ◽  
The North ◽  
Central Alborz ◽  
Mosha Fault

Abstract. Several active faults affect the Central Alborz, Northern Iran. The main active faults in the region are the North Tehran and the Mosha faults and their westward continuation, the Taleghan fault. Among these the Mosha fault is the most active fault in Central Alborz. The piezomagnetic field has been inspired by many investigations in the earthquake prediction studies and has been reported in the literature. Several theories proposed for relating piezomagnetic changes into magnetic signals accompanying earthquakes in the vicinity of a fault. In this study based on an analytical solution for the elementary piezomagnetic potentials due to an inclined rectangular fault within a semi-infinite elastic medium a computer program has been developed. This program has been used for evaluation of the rotational piezomagnetic changes along the Mosha fault using different earthquakes with specific magnitudes and at the presence of three different geomagnetic main fields. The magnetic data acquired recently at the study area has been used during the modeling. The first result that can be inferred from this study is that rotational piezomagnetic anomalies are completely localized at the fault tips. So for detection of this anomaly the magnetic instruments should be installed at these locations. The other important element which has been investigated was the amount of slip along the fault, which shows anomaly intensification by increase in the amount of slip.

Ras al Khaimah: further archaeological discoveries

Antiquity ◽  
1976 ◽  
Vol 50 (200) ◽  
pp. 216-222
Author(s):  
Beatrice De Cardi
Keyword(s):  
United Arab Emirates ◽  
The State ◽  
Focused Attention ◽  
North East ◽  
The North ◽  
History Of ◽  
The City

Ras a1 Khaimah is the most northerly of the seven states comprising the United Arab Emirates and its Ruler, H. H. Sheikh Saqr bin Mohammad al-Qasimi, is keenly interested in the history of the state and its people. Survey carried out there jointly with Dr D. B. Doe in 1968 had focused attention on the site of JuIfar which lies just north of the present town of Ras a1 Khaimah (de Cardi, 1971, 230-2). Julfar was in existence in Abbasid times and its importance as an entrep6t during the sixteenth and seventeenth centuries-the Portuguese Period-is reflected by the quantity and variety of imported wares to be found among the ruins of the city. Most of the sites discovered during the survey dated from that period but a group of cairns near Ghalilah and some long gabled graves in the Shimal area to the north-east of the date-groves behind Ras a1 Khaimah (map, FIG. I) clearly represented a more distant past.

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