Preface to the special issue “Triggered and induced seismicity: probabilities and discrimination”
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Triggered and induced seismicity are the earth response to transient non-tectonic phenomena. In a common definition, a triggered earthquake is assumed as an event whose occurrence is anticipated in view of the background seismicity rate. The triggering process, caused by a transient phenomena, only concerns the nucleation of a small region of the rupture area, whereas the entire rupture is controlled by the background stress. An induced event, in change, is entirely (e.g. in terms of rupture size and energy released) controlled by its causative origin and would not occur without it. A complementary, stress-based approach to define the boundary among triggered and induced seismicity was discussed by McGarr and Simpson (1997), in the specific framework of anthropogenic seismicity. According to their classification, a broader term of “stimulated” seismicity could be used to describe both triggered and induced seismicity.
Transients which can induce or trigger seismicity can either be of natural or anthropogenic origin. Natural phenomena which can favour seismicity include rain, snow, pore pressure changes, magma dikes, and geothermal and volcanic processes. Earthquake–earthquake interactions may also be considered as a specific case of triggered seismicity. A second, important group of induced and triggered events are those of anthropogenic origin. Different human-related activities may favour, or inhibit, the earthquake occurrence, e.g. by inducing local stress perturbations, affecting the subsurface strain, or inducing changes in the pore pressure. Known cases of human operations which can induce seismicity or microseismicity include mining operations and mass shifts, water reservoir impoundment, drilling, oil- and gas-field exploitation, hydro-fracturing, and fluid injection and removal.
Special issues on induced/triggered seismicity have been frequently published. However, it is the first time that a special issue on this topic is published on the Journal of Seismology. Among the specific novelties which characterize this issue are the specific seismological viewpoints of collected contributions, the aim to discuss the natural/induced/triggered seismicity discrimination problem, and the focus on probabilistic methodological approaches and applications. This issue recollects recent significant scientific advances in the monitoring, analysis, and discrimination of induced and triggered earthquakes, as well as specific applications to different induced and triggered seismicity cases, both anthropogenic and driven by natural processes. Since no clear rules have so far been accepted by the scientific community regarding the discrimination between natural, triggered, and induced earthquakes, the issue has a specific focus on the discrimination problem and has the wish to contribute and further stimulate the scientific discussion in this sense. A second relevant topic concerns the development and adoption of probabilistic approaches, both for the determination of the origin of seismicity, its source characteristics, and its relation to other natural phenomena and human activities, and to evaluate seismic hazard for induced and triggered seismicity.
The collected manuscripts mostly focus on anthropogenic induced seismicity, although the case of natural induced seismicity by dikes is also treated (Passarelli et al. 2012). Anthropogenic seismicity is discussed for mining operations (Rudziński and Dębski 2012; Cesca et al. 2012), water reservoirs (Mallika et al. 2012), gas field exploitation (Kraaijpoel and Dost 2012; Cesca et al. 2012), and geothermal systems (Barth et al. 2012; Plenkers et al. 2012; Häge et al. 2012; Dinske and Shapiro 2012).
Following a scientific and geophysical viewpoint, different techniques are developed, discussed or applied, including source location (Rudziński and Dębski 2012; Häge et al. 2012; Husen et al. 2012), moment tensor inversion (Cesca et al. 2012), source parameters estimation (Husen et al. 2012; Barth et al. 2012), waveform cross correlation (Plenkers et al. 2012), catalogue assessment, and magnitude distribution (Dinske and Shapiro 2012; Häge et al. 2012; Barth et al. 2012). Finally, results from laboratory studies associated to pore pressure changes are discussed in Turuntaev et al. (2012).
The discrimination problem is treated here in different works. Cesca et al. (2012) and Passarelli et al. (2012) propose different probabilistic approaches for the discrimination among natural and induced/triggered events. A probabilistic approach is also discussed in Barth et al. (2012), which focuses on the assessment of the probability to exceed given magnitude thresholds in different injection phases. Klose (2012) discusses the relation between mass shifts and different induced earthquake source parameters and recompiles a catalogue of relevant induced/triggered events. Finally, the contribution of Dahm et al. (2012), which summarizes an open discussion involving a large number of experts and researchers, attempts to describe the state of the art with respect to the problem of natural, induced, and triggered earthquake discrimination to set up possible guidelines and a framework for the development of a discrimination/decision scheme, and presents possible modules that may be implemented there.
The catalogue and map of induced seismicity in Europe has been recompiled thanks to several contributions. We wish to thank here the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR; Germany), the Koninklijk Nederlands Meteorologisch Instituut (KNMI; The Netherlands), the Czech Academy of Sciences (Czech Republic), the Institute of Geodynamics, National Observatory of Athens (Greece), and the Instituto Geográfico Nacional (IGN; Spain), which seismic catalogues were used to compile and complement the current version of the IS catalogue. We are also thankful to E. Buforn, J. R. Grasso, S. Lasocki, G. Mutke, B. Orlecka-Sikora, J. Wassermann, and J. Zednik for their personal contributions. Information on specific events have been obtained from the following scientific publications: Rothé (1970), Buforn and Udias (1979), Stein et al. (1982), Batini et al. (1985), Grasso and Wittlinger (1990), Grasso et al. (1992), Gupta (1992), Ruiz et al. (2006), Torcal et al. (2005), Cesca et al. (2011), and Klose (2012).
- Barth A, Wenzel F, Langenbruch C (2012) Probability of earthquake occurrence and magnitude estimation in the post shut-in phase of geothermal projects. J Seismol. doi: 10.1007/s10950-011-9260-9
- Cesca S, Rohr A, Dahm T (2012) Full moment tensor inversion and decomposition to discriminate induced seismicity. J Seismol. doi: 10.1007/s10950-012-9305-8
- Dahm T, Becker D, Bischoff M, Cesca S, Dost B, Fritschen R, Hainzl S, Klose CD, Kühn D, Lasocki S, Meier T, Ohrnberger M, Rivalta E, Wegler U, Husen S (2012) Recommendations on the discrimination between human-related and natural seismicity. J Seismol. doi: 10.1007/s10950-012-9295-6
- Dinske C, Shapiro SA (2012) Seismotectonic state of reservoirs inferred from magnitude distributions of fluid-induced seismicity. J Seismol. doi: 10.1007/s10950-012-9292-9
- Häge M, Blascheck P, Joswig M (2012) EGS hydraulic stimulation monitoring by surface arrays—location accuracy and completeness magnitude: the Basel Deep Heat Mining Project case study. J Seismol. doi: 10.1007/s10950-012-9312-9
- Husen S, Kissling E, von Deschwanden A (2012) Induced seismicity during the construction of the Gotthard Base Tunnel, Switzerland: hypocenter locations and source dimensions. J Seismol. doi: 10.1007/s10950-012-9313-8
- Klose CD (2012) Correlations between medium- to large-size earthquakes and man-made mass shifts on the Earth's upper crust. J Seismol (in press)Google Scholar
- Kraaijpoel D, Dost B (2012) Implications of salt-related propagation and mode conversion effects on the analysis of induced seismicity. J Seismol. doi: 10.1007/s10950-012-9309-4
- Mallika K, Gupta H, Shashidar D, Purnachandra Rao N, Yadav A, Rohilla S, Satyanarayana HVS, Srinagesh D (2012) Temporal variation of b value associated with the M 4 earthquakes in the reservoir-triggered seismic environment of the Koyna–Warna region, Western India. J Seismol. doi: 10.1007/s10950-012-9318-3
- McGarr A, Simpson D (1997) Keynote lecture: a broad look at induced and triggered seismicity, “Rockbursts and seismicity in mines”. In: Gibowicz SJ, Lasocki S (eds) Proceeding of 4th international symposium on rockbursts and seismicity in mines, Poland, 11–14 August 1997. A.A. Balkema, Rotterdam, pp 385–396Google Scholar
- Passarelli L, Maccaferri F, Rivalta E, Dahm T, Boku EA (2012) A probabilistic approach for the classification of earthquakes as ‘triggered’ or ‘not triggered’. J Seismol. doi: 10.1007/s10950-012-9289-4
- Plenkers K, Ritter JRR, Schindler M (2012) Low signal-to-noise event detection based on waveform stacking and cross correlation: application to a stimulation experiment. J Seismol. doi: 10.1007/s10950-012-9284-9
- Rudziński L, Dębski W (2012) Extending the double difference location technique for mining applications. J Seismol. doi: 10.1007/s10950-012-9322-7
- Turuntaev SB, Eremeeva EI, Zenchenko EV (2012) Laboratory study of microseismicity spreading due to pore pressure change. J Seismol. doi: 10.1007/s10950-012-9303-x