Excitation of earthquakes by microseismic noise and weather phenomena (original) (raw)
Related papers
Encyclopedia of earth sciences, 2020
Seismology is usually devoted to the investigation of tectonic earthquakes and imaging of the solid structure of the Earth. But with the improvement of seismometers and the explosion of the continuous recording of the ground motion by broadband seismic networks, other phenomena can be investigated. Since seismometers are sensitive to any kind of ground displacement, small events hidden in the noise can be detected. A large part of these small events is related to the interaction or the coupling of the surface of the solid Earth with its surficial unconsolidated solids, fluid/gas enveloppes (ocean and atmosphere). Iceberg calving, glacier dynamics, landslides, snow avalanches, hurricanes, ocean waves belong to this kind of environmental events, able to generate observable seismic signals. Microseisms permanently excited by the interaction of gravity waves and swells in oceans, fluvial seismic signals make it necessary to use statistical approaches for extracting useful information on the source processes in a broad frequency range. In contrast to microseisms, other events are episodic, deterministic, some of them well located in space and time, can be individually investigated. The study of all these natural phenomena giving rise to observable seismic signals constitute the field of environmental seismology. Due to the faintness of the associated signals, new methods and techniques have been used. For deterministic events, beamforming methods, time-reversal methods or its less general form, back-projection technique (see Larmat et al., this issue for all references), have been applied to locate them in space and time. Microseisms were investigated since Wiechert (1904) and physical processes to explain them were proposed many decades ago (Longuet-Higgins, 1950, Hasselman, 1963). For a stochastic approach of ambient noise, the cross-correlation methods of signals between two seismic stations are now routinely used and make it possible to retrieve the empirical Green’s function (impulse response of the propagating medium) between these two stations (see Campillo et al., this issue). They are particularly well suited for monitoring physical parameters such as variation in the subsoil temperature, aquifers, climate and global changes. Environmental seismology can be distinguished from “anthropic seismology”, including the study of seismic signals associated with anthropic activity, such as nuclear, mining explosions, attacks, triggered events, urban seismology (traffic, footquakes …) eventhough similar methods can be used to study them.
Izvestiya, Physics of the Solid Earth, 2008
The paper generalizes the experience accumulated in studies of microseismic noise in the period range from 1 to 300 min observed during time intervals preceding a few strong earthquakes. This frequency range is the least studied and occupies an intermediate position between low frequency seismology and investigations of slow geophysical processes. The range includes oscillations induced by atmospheric and oceanic processes and various modes of the Earth's free oscillations excited by very strong earthquakes. The main attention in the paper is given to the background behavior of microseisms, which contains continuous present arrivals from near weak and far strong and moderate earthquakes. The paper focuses on the examination of synchronization effects arising in joint multivariate analysis of information from several stations with estimation of multifractal spectra of singularity and multidimensional spectral measures of coherent behavior of singularity spectral parameters. The problem of using the synchronization effects of microseismic background in the search for new precursors of strong earthquakes is discussed. PACS numbers: 91.30.Bi
Analysis of microseismic events from a stimulation at Basel, Switzerland
GRC …, 2007
The researchers from Tohoku University, Japan, analyzed microseismic events collected during a stimulation at Basel, Switzerland in December 2006. More than 2,000 events from over 13,000 triggers were located by the single event determination (SED) method, by joint hypocenter determination (JHD), and by the coherence-collapsing method (COH-COL). The located events define a seismic cloud with a sub-vertical structure and an azimuth of N159°E, which is similar to that at Soultz. The percentage of multiplets among the located events was 75%, which was higher than that at Soultz. The spatio-temporal analysis of the microseismic locations showed clear shut-in events around the stimulated zone and continuous seismic activity after pumping, suggesting that the stress state around the reservoir was nearly critical for shear slip.
Introduction to this special section: Passive seismic and microseismic—Part 2
The Leading Edge, 2012
An introduction to this special section: Passive seismic and microseismic-Part 2 W elcome to the second half of TLE's two-part special section on passive seismic and microseismic. This month, we focus again on monitoring hydraulic fracturing with microseismic with five articles, but also expand beyond "micro"seismicity, to include unintended "induced" seismicity that may occur during injection. Five articles in this special section focus on induced-seismicity topics. In this introduction, we will highlight various issues related to undesired induced seismicity which may be caused by hydraulic fracturing and deep, underground salt water disposal. Why should you care about induced seismicity? The large increase in unconventional plays and hydraulic fracturing, discussed in the November special section introductory article (Goodway, 2012), has been accompanied with an increase in the generation of wastewater, which is a byproduct resulting from flowback after the stimulation procedure. Induced seismicity from the wastewater injection is extremely rare, occurring in less than 1% of the wells (NAS report, 2012, Shemeta et al., this issue). Induced seismicity (M>1) associated with hydraulic fracturing is even more rare. However rare, and regardless of the cause, induced seismicity
Frequency ranges and attenuation of macroseismic effects
Geophysical Journal International, 2017
Macroseismic intensity is assessed on the basis of the effects caused by an earthquake. These effects reflect the expression of both the intensity and frequency of the ground motion, thus complicating prediction equation modelling. Here we analysed data of several macroseismic transitory effects caused by recent Italian earthquakes in order to study their attenuation as a function of magnitude and hypocentral distance and to obtain a specific prediction equation, of simple functional form, that could be applied to each of the effects under analysis. We found that the different attenuation behaviours could be clearly defined by the values of the specially formulated magnitude-distance scaling ratio (S), thus allowing to group the effects on the basis of the S value. The oscillation of hanging objects and liquids, together with the feeling of dizziness, were separated from most other variables, such as the effects of the earthquake on small objects, china and windows, which were caused by a vibration of higher frequency. Besides, the greater value of S, associated with the perception of the seismic sound, explained the peculiarity of this phenomenon. As a result, we recognized the frequency range associated with each effect through comparisons with the ground motion prediction equations and, in particular, with the 5 per cent damped horizontal response spectra. Here we show the importance of appropriately selecting the diagnostic elements to be used for intensity assessment in order to improve the correlation with ground motion.
On the interpretation of resonance frequencies recorded during microseismic experiments
2013
Summary Continuous passive seismic recordings during hydraulic fracture treatments can be used to map the frequency content of wavefields emitted by microseismic events during fluid injection. Recent studies have shown that the frequency content of continuous recordings contains information on the fluid injection. In particular, spectral lines can be caused by different phenomena leading to similar resonance frequencies. The first step is then to identify and separate the possible sources (receiver, path and source effects) to facilitate the interpretation of the specific resonances due to fluid injection. We here report two case studies where resonance frequencies are detected. In the case of the first case study, some low-frequency (5-50 Hz) resonance frequencies are found on the borehole geophones as well as two arrays of broadband stations on the surface. The spatial distribution of the stations that have recorded these resonances suggests that they could originate from the vert...
Releasing of tectonic stresses by using microseismogenic phenomena
Геофизический журнал (Geofizicheskiy Zhurnal), 2014
Description of amplitude and frequency modulations of standing water waves (seiches) is presented. It is shown that fluctuations of microseisms, origin by seiches, may be used to discharge the tectonic stress. Developed ways to optimize them.