induced earthquakes
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2022 ◽  
Vol 22 (1) ◽  
pp. 41-63
Author(s):  
Janneke van Ginkel ◽  
Elmer Ruigrok ◽  
Jan Stafleu ◽  
Rien Herber

Abstract. Earthquake site response is an essential part of seismic hazard assessment, especially in densely populated areas. The shallow geology of the Netherlands consists of a very heterogeneous soft sediment cover, which has a strong effect on the amplitude of ground shaking. Even though the Netherlands is a low- to moderate-seismicity area, the seismic risk cannot be neglected, in particular, because shallow induced earthquakes occur. The aim of this study is to establish a nationwide site-response zonation by combining 3D lithostratigraphic models and earthquake and ambient vibration recordings. As a first step, we constrain the parameters (velocity contrast and shear-wave velocity) that are indicative of ground motion amplification in the Groningen area. For this, we compare ambient vibration and earthquake recordings using the horizontal-to-vertical spectral ratio (HVSR) method, borehole empirical transfer functions (ETFs), and amplification factors (AFs). This enables us to define an empirical relationship between the amplification measured from earthquakes by using the ETF and AF and the amplification estimated from ambient vibrations by using the HVSR. With this, we show that the HVSR can be used as a first proxy for site response. Subsequently, HVSR curves throughout the Netherlands are estimated. The HVSR amplitude characteristics largely coincide with the in situ lithostratigraphic sequences and the presence of a strong velocity contrast in the near surface. Next, sediment profiles representing the Dutch shallow subsurface are categorised into five classes, where each class represents a level of expected amplification. The mean amplification for each class, and its variability, is quantified using 66 sites with measured earthquake amplification (ETF and AF) and 115 sites with HVSR curves. The site-response (amplification) zonation map for the Netherlands is designed by transforming geological 3D grid cell models into the five classes, and an AF is assigned to most of the classes. This site-response assessment, presented on a nationwide scale, is important for a first identification of regions with increased seismic hazard potential, for example at locations with mining or geothermal energy activities.


Author(s):  
A. Malovichko ◽  
N. Petrova ◽  
I. Gabsatarova ◽  
R. Mikhailova ◽  
V. Levina ◽  
...  

The review of the Northern Eurasia seismicity for 2015 includes a description of seismic networks, the results of analysis of the seismic regime and individual noticeable earthquakes in 16 regions of Russia and neighbouring countries. Seismic monitoring was carried out by the networks of seismic station of Russia, Azerbaijan, Armenia, Belarus, Kazakhstan, Kyrgyzstan, Latvia, Moldova, Turkmenistan, Tajikistan, Uzbekistan, Ukraine, including 599 digital, 7 analogue stations and eight seismic groups. In 2015, these networks registered about 27 thousand tectonic earthquakes, over 6 thousand volcanic earthquakes, 599 explosions, 23 mountain-tectonic shocks and induced earthquakes. Focal mechanisms of 592 earthquakes were determined, the information on manifestations of 449 perceptible earthquakes was collected. 26 shocks were felt in settlements of Northern Eurasia with an intensity Ii≥5. According to estimates of the annual number and released seismic energy in 2015 in comparison with the long-term characteristics of the seismic regime, the seismic process in most regions of Northern Eurasia proceeded in the “background” regime. An exception is Tajikistan and adjacent territories, where two strong earthquakes occurred – the Hindu Kush earthquake on October 26 with Mw=7.5, h=230 km in northern Afghanistan, near the border with Tajikistan, and the Sarez earthquake on December 7 with Mw=7.2, Ms=7.6, h=20 km in Tajikistan. Both earthquakes were accompanied by numerous aftershocks and were felt in Tajikistan with intensities Imax=7 and Imax=7–8 respectively, on the MSK-64 scale. Notable event on the territory of Northern Eurasia in 2015 is the emergence of the Muyakan sequence of earthquakes, the largest for the period of instrumental observations in the region "Baikal and Transbaikalia", as a result of which the number of recorded earthquakes in the region quadrupled concerning 2014. The other interesting fact is occurrence of tangible earthquakes in the regions, traditionally considered weakly seismic – near the Semipalatinsk test area in Eastern Kazakhstan (Chingiz earthquake on January 20, Ms=4.1, I0=5–6), in the Middle Urals (Middle Ural earthquake on October 18 with ML=4.7, I0=6) and in the southwest of East -European platform (Poltava earthquake on February 3 with KR=10.7, I0=6).


2021 ◽  
Vol 946 (1) ◽  
pp. 012011
Author(s):  
Yu V Fedotova ◽  
P A Anikin ◽  
M I Potapchuk

Abstract Geodynamic activity of the Earth’s crust depends on the parameters of the movement of lithospheric plates and stress fields, both inherited in aseismic areas and modified in seismic active ones. Geomechanical processes occur in rock mass under the influence of various natural (endogenous and exogenous) and man-made (anthropogenic) factors. The degree of influence of these factors on the change in the energy saturation of blocks of various ranks will depend on various factors. In the geological environment of natural and man-made systems, there are dynamic phenomena of various energy levels from acoustic noise (microseismic) to rockburst and mining-induced earthquakes, that is, there is always a geodynamic risk in the geological environment of natural and man-made systems, especially in mining ones. The conditions of the geodynamic risks occurrence at specific deposits are considered on the example of rockburst hazardous deposits in the Far Eastern region of the Russian Federation. The influence of natural seismic activity on the realization of mining-induced seismicity is shown.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hongyu Yu ◽  
Rebecca M. Harrington ◽  
Honn Kao ◽  
Yajing Liu ◽  
Bei Wang

AbstractAseismic slip loading has recently been proposed as a complementary mechanism to induce moderate-sized earthquakes located within a few kilometers of the wellbore over the timescales of hydraulic stimulation. However, aseismic slip signals linked to injection-induced earthquakes remain largely undocumented to date. Here we report a new type of earthquake characterized by hybrid-frequency waveforms (EHWs). Distinguishing features from typical induced earthquakes include broader P and S-pulses and relatively lower-frequency coda content. Both features may be causally related to lower corner frequencies, implying longer source durations, thus, either slower rupture speeds, lower stress drop values, or a combination of both. The source characteristics of EHWs are identical to those of low-frequency earthquakes widely documented in plate boundary fault transition zones. The distribution of EHWs further suggests a possible role of aseismic slip in fault loading. EHWs could thus represent the manifestation of slow rupture transitioning from aseismic to seismic slip.


Author(s):  
Annukka E. Rintamäki ◽  
Gregor Hillers ◽  
Tommi A. T. Vuorinen ◽  
Tuija Luhta ◽  
Jonathan M. Pownall ◽  
...  

Abstract We present the deployment of a seismic network in the Helsinki capital area of Finland that was installed to monitor the response to the second stimulation phase of an ∼6-kilometer-deep enhanced geothermal system in 2020. The network consists of a dozen permanent broadband stations and more than 100, predominantly short-period, temporary stations. This 2020 deployment is characterized by a mix of single stations and arrays with diverse configurations. It covers a larger area and exhibits a smaller azimuthal gap compared with the network that monitored the first stimulation in 2018. We surveyed the outcropping rocks at one of the large array sites to study surface expressions of shear or weakness zones that are possibly connected to the stimulated volume at depth. We link the relatively large number of macroseismic reports received during the stimulation to an increased public awareness of the project together with an increased sensitivity because the second stimulation occurred during the local COVID-19 mobility restrictions. The spatial distribution of the reports seems to be controlled by the radiation pattern of the induced earthquakes and hence by the stress state in the reservoir. The continuous records contain strong energy at high frequencies above 50 Hz that is attributed to anthropogenic processes in the densely populated urban area. However, the exceptionally low attenuation of the bedrock yields good signal-to-noise ratio seismograms of the induced small events, the largest of which was magnitude ML 1.2. The signal quality of the obtained noise correlation functions is similarly very good. The data set has been collected to underpin a wide range of seismic analysis techniques for complementary scientific studies of the evolving reservoir processes and the induced event properties. These scientific studies should inform the legislation and educate the public for transparent decision making around geothermal power generation.


Author(s):  
Tianyang Li ◽  
Yu Jeffrey Gu ◽  
Jingchuan Wang ◽  
Ruijia Wang ◽  
Javad Yusifbayov ◽  
...  

Abstract Although hydraulic fracturing-induced earthquakes have been widely reported in Alberta, Canada, only one seismic cluster (the Cordel Field) has thus far been linked to wastewater disposal (WD). In this study, we report a statistically significant spatiotemporal correlation between recent earthquakes and nearby WD wells near Musreau Lake—the second disposal-induced earthquake swarm in Alberta. This newly occurred swarm contains five events with local magnitudes ML>3 from January 2018 to March 2020, forming into three tightly spaced clusters. The refined locations and focal mechanisms suggest a ∼10 km long northwest–southeast-trending rupture along the northern Rocky Mountains that developed over time, during which both poroelastic effects and static stress transfer played key roles. Through a statistical analysis of all reported induced earthquake clusters in the western Canada sedimentary basin (WCSB), we propose a linear predictive relationship (i.e., the “Interpolated Strike Orientation” model) between fault rupture direction and fault distance to the Rocky Mountains. This observation-based model, which is supported by both the focal mechanisms of the natural earthquakes and the nearby northwest-striking geological faults, is a new and useful reference for future assessments of seismic hazard in the WCSB.


2021 ◽  
Author(s):  
Andrea Borgia ◽  
Alberto Mazzoldi ◽  
Luigi Micheli ◽  
Giovanni Grieco ◽  
Massimo Calcara ◽  
...  

Production of geothermal energy for electricity at Amiata Volcano uses flash-type power plants with cooling towers that evaporate much of the geothermal fluid to the atmosphere to condense the geothermal vapour extracted. Because the flash occurs also within the geothermal reservoir, it causes a significant depressurization within it that, in turns, results in a drop of the water table inside the volcano between 200 and 300 m. The flow rates of natural springs around the volcano have also substantially decreased or ceased since the start of geothermal energy exploitation. Continuous recording of aquifer conditions shows substantial increases in salinity (>20%) and temperature (>2°C) as the water table falls below about 755–750 m asl. In addition to hydrologic impacts, there are also a large numbers of induced earthquakes, among which the ML 3.9, April 1, 2000 earthquake that generated significant damage in the old villages and rural houses. Relevant impacts on air quality occur when emissions are considered on a per-MW basis. For example, CO2+CH4 emissions at Amiata are comparable to those of gas-fired power plants (1), while the acid-rain potential is about twice that of coal-fired power plants. Also, a significant emission of primary and secondary fine particles is associated with the cooling towers. These particles contain heavy metals and are enriched in sodium, vanadium, zinc, phosphorous, sulphur, tantalium, caesium, thallium, thorium, uranium, and arsenic relative to comparable aerosols collected in Florence and Arezzo (2). Measurements have shown that mercury emitted at Amiata comprises 42% of the mercury emitted from all Italian industries, while an additional comparable amount is emitted from the other geothermal power plants of Tuscany (3). We believe that the use of air coolers in place of the evaporative cooling towers, as suggested in 2010 by the local government of Tuscany (4), could have and can now drastically reduced the environmental impact on freshwater and air. On the opposite side of the coin, air-coolers would increase the amount of reinjection, increasing the risk of induced seismicity. We conclude that the use of deep borehole heat exchangers could perhaps be the only viable solution to the current geothermal energy environmental impacts.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Serge A. Shapiro ◽  
Kwang-Hee Kim ◽  
Jin-Han Ree

AbstractA damaging Mw5.5 earthquake occurred at Pohang, South Korea, in 2017, after stimulating an enhanced geothermal system by borehole fluid injections. The earthquake was likely triggered by these operations. Current approaches for predicting maximum induced earthquake magnitude ($${M}_{\max }$$ M max ) consider the volume of the injected fluid as the main controlling factor. However, these approaches are unsuccessful in predicting earthquakes, such as the Pohang one. Here we analyse the case histories of induced earthquakes, and find that $${M}_{\max }$$ M max scales with the logarithm of the elapsed time from the beginning of the fluid injection to the earthquake occurrence. This is also the case for the Pohang Earthquake. Its significant probability was predictable. These results validate an alternative to predicting $${M}_{\max }$$ M max . It is to monitor the exceedance probability of an assumed $${M}_{\max }$$ M max in real time by monitoring the seismogenic index, a quantity that characterizes the intensity of the fluid-induced seismicity per unit injected volume.


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