Geothermal fluids circulation at Caldas do Moledo area, Northern Portugal: geochemical and isotopic signatures

Marques, José Frederico; Marques, Jorge Espinha; Carreira, Paulà M.; Graça, R. C.; Aires-Barros, Luís A.; Carvalho, Julia; Chaminé, Helder I.; Borges, Frederico Sodré

doi:10.1046/j.1468-8123.2003.00059.x

Cited by 29 publications

(5 citation statements)

References 27 publications

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“…Those characteristics have been linked to the effects of fluid migration (e.g., Mogi 1962;Scholz 1968;Hainzl and Fischer 2002;Hainzl et al 2013;Crespo-Martin et al 2021). This hypothesis is also supported by: A.-The well-known existence of thermal springs and even crustal fluids in the NW Iberian Peninsula (e.g., Almeida 1982, Pérez et al 1996Marques et al 2003;López et al 2015), linked to deeply fractured crust and active faults. These studies propose that the excess of mantle helium-3 recorded in the groundwater occurs along the seismogenic faults, representing channels for the potential escape of mantle.…”

Section: Discussionmentioning

confidence: 88%

Testing potential trigger mechanisms for seismicity in Sarria-Triacastela-Becerreá (Lugo seismic sequences) NW Iberian Peninsula, Spain

Crespo-Martín

Martín-González²,

Hainzl³

et al. 2022

J Seismol

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The unprecedented and long-lasting seismicity of Triacastela (over 25 years) attracted the interest of the research community on this stable continental region (SCR), particularly after the anomalously high 5.1 and 4.9 Mw earthquakes compared to the regional standards. The high rainfall and tide rates of this region compared to the rest of the Iberian Peninsula, in addition to the recognized existence of thermal springs and crustal fluids, motivated us to test these sources of hydroseismicity as a potential trigger mechanism for the observed seismicity in Triacastela. Based on network upgrades, we have gathered the seismic catalog in two periods for analysis (before and after year 2002). Before 2002, neither a diffusion-type earthquake migration nor any significant statistical correlation between the seismicity rates and rainfall or tides is found. After 2002, some clusters migrate to the south, suggesting the presence of fluid migration during earthquake swarms, but no diffusion-type migration is observed on longer time scales. Furthermore, we find correlation coefficients close to zero, indicating that rainfall and tides can be excluded as driving mechanisms. However, the seismic upward migration, a high b-value (1.2), and a low aftershock-productivity parameter (α=0.9) observed in this period support the hypothesis of upward fluid migration through fracture zones. The presence of Mantellic helium-3 along the seismogenic faults and the increase of geochemical precursors in the groundwater previously to 1995 and 1997 mainshocks further support deep fluids as a source for the observed induced fluid migration seismicity in Triacastela. Article Highlights:• Swarms, upward migration, high b-value, and low α-value after 2002 suggest a fluid influence on Triacastela seismicity.• Pearson correlations close to zero reject rainfall and tides as driving mechanisms of Triacastela seismicity.• The mantellic helium-3 in groundwaters, the geochemical precursors rise and elements mobility over faults evoke deep fluids migration.

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Section: Discussionmentioning

confidence: 88%

Testing potential trigger mechanisms for seismicity in Sarria-Triacastela-Becerreá (Lugo seismic sequences) NW Iberian Peninsula, Spain

Crespo-Martín

Martín-González²,

Hainzl³

et al. 2022

J Seismol

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“…4 and Table 3). In this region, the existence of thermal springs is well known, and some studies correlate the deep crustal and even mantellic fluids with the seismicity in this area (Pe´rez et al 1996;Marques et al 2003;López et al 2015). These findings could support the result of our statistical analysis and suggest fluid migration as a possible source of seismicity.…”

Section: O T H E R S E I S M I C C L U S T E R S I N T H E N W I B E R I a N P E N I N S U L Amentioning

confidence: 99%

Time-dependent and spatiotemporal statistical analysis of intraplate anomalous seismicity: Sarria-Triacastela-Becerreá (NW Iberian Peninsula, Spain)

Crespo-Martín

Martín-González

Yazdi

et al. 2021

Geophysical Journal International

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Summary The Sarria-Triacastela-Becerreá seismicity is located in an intraplate region considered seismically stable, but in 1995 started an unprecedented earthquake activity in the area. Since then an anomalous long-term continuous seismicity remains until now in the same location. Despite the long-term seismicity and the large magnitudes for the region standards (5.1 Mw), the origin and mechanisms of this seismicity remains unclear. The isolation of background from the mainshock-aftershock contribution by means of the application of the Epidemic Type Aftershock Sequences (ETAS) model, the spatial depiction, and the resemblance to near seismic regions allow us to identify several seismicity behaviours. From 1995 to 1998/99, the seismicity in this location mainly consists of intensive and deeper earthquake sequences linked to the 1995 and 1997 mainshocks. Our results suggest that the mainshocks triggered aftershocks and additionally initiated or facilitated aseismic processes. A likely scenario is that the mainshocks broke a sealed source at depth allowing a subsequent intrusion of high-pressurized fluids from depth. The resemblance of this period with Zamora seismic characteristics proposes that Triacastela seismicity was also initiated by tectonic activity. From 1998/99 to 2018, a change in seismicity is observed, the background contribution took control and swarm-type activity is predominant. While the earthquake rate decreases, the relative background contribution goes up. Actually, after 2013 the clusters almost disappear and background contribution achieves 55 per cent of the total activity. The spatial migration to the southeast and the upward trend to shallower depth support fluid migration as possible driving mechanism responsible for the transient seismicity in this period. The swarm-type activity in Triacastela in later periods and the resemblance of b-values with Ponte Caldelas and Ventaniella seismicity suggest that the seismicity in Triacastela is related to fluid migration and the reactivation of fractured areas. We propose that the mechanism of this anomalous and long-term seismicity in Triacastela is the mix of different mechanisms, starting with the tectonic seismicity, generated during the 1995 and 1997 seismic sequences, which initiated a fluid upward migration through fractured crustal fault patches, observed after 1998–99, and responsible for the seismicity during the following 20 years.

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“…Otherwise, minor and trace element composition ones were Al, As, B, Ba, Br, Co, Cr, Cs, Cu, Fe, I, Li, Mn, Mo, Ni, Rb, Sr, Tl and Zn [9]. Typical geothermal fluids, with local shallow ground waters, were characterized by a relatively high concentration of K, Ca, NO 3 , SO 4 , and Cl [10]. The waters are mostly acid with pH between 1.5 and 7.9 caused by elevated SO 4 between 10 and 5066 ppm and are elevated in most metals including Fe (0.05-753 ppm) and Al (0.03-390 ppm) but low in Cl (1.4-17.9 ppm) [11].…”

Section: Introductionmentioning

confidence: 99%

Leakage Current and Pollutant Properties of Porcelain Insulators from the Geothermal Area

Waluyo¹,

Sinisuka

Suwarno

et al. 2009

ECTI-EEC

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This manuscript presents the experimental results of a new-clean and seven geothermal naturally polluted outdoor porcelain insulators. These insulators were tested in a hermetically sealed chamber, where their leakage currents and applied voltages were measured with a storage digital oscilloscope. The measured data could be recorded oscilloscope and transferred to a computer, saved in softcopy forms. FFT was used to analyze the leakage current waveforms, and correlation coe±cient matrix and principal component analysis (PCA) were used to analyze the relation among parameters. It was also carried out EDAX tests of insulator adhered pollutant. The results indicated that the power factors and leakage current amplitudes closed to humidity, the phase angle closed to THD, and temperature opposited the humidity. The ratios of insulator impedance on the high and low humidity were ranged from 0.8696 until 0.1343. The small insulator impedance ratios were rearched on the ¯rst and seventh withdrawals, i.e. 0.1363 and 0.1343 respectively. On these insulators, THD ratios on the same conditions were 0.3739 and 0.4598 respectively. These phenomena were caused by dry season, which amount of pollutant stuck on the insulator surfaces signi¯cantly. On the high humidity, the minimum phase angles ranged between 66.8 and 25.7 degrees. Sulfur chemical element was found in medium composition on the pollutant.

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Geothermal fluids circulation at Caldas do Moledo area, Northern Portugal: geochemical and isotopic signatures

Cited by 29 publications

References 27 publications

Testing potential trigger mechanisms for seismicity in Sarria-Triacastela-Becerreá (Lugo seismic sequences) NW Iberian Peninsula, Spain

Testing potential trigger mechanisms for seismicity in Sarria-Triacastela-Becerreá (Lugo seismic sequences) NW Iberian Peninsula, Spain

Time-dependent and spatiotemporal statistical analysis of intraplate anomalous seismicity: Sarria-Triacastela-Becerreá (NW Iberian Peninsula, Spain)

Leakage Current and Pollutant Properties of Porcelain Insulators from the Geothermal Area

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