Geological Map 197 The World Stress Map

Knowledge of the stress field in the Earth's crust is a key compressional stress), and Sv (vertical stress). The minimum stress issue for the understanding of geodynamic processes, information needed for each data record is the SH orientation. Thus, mapping of the WSM database is proceeded by plotting the SH ori- seismic hazard assessment, and stability of underground entation and the tectonic regime, even though a large number of data openings such as waste disposals, tunnels, mines or records in the database provide more stress information. wells, and reservoir management. The World Stress Map project is a collaborative project of academia, Methods for determining stress orientations industry and governmental organizations that aims to The present-day stress information presented in the WSM is understand the states and sources of tectonic stresses in estimated from a variety of stress indicators of four categories: earth- the Earth's crust. We present the World Stress Map at quake focal mechanism solutions, stress-induced borehole break- outs, in-situ stress measurements and geologic indicators. Each tech- 1:46,000,000 scale as a result of more than two decades nique reflects the stress field of different rock volumes ranging from of international collaboration. The map reveals that the 10-3 to 109 m3 and different depths ranging from near surface down first-order pattern of stress is of plate-wide scale, indi- to 40 km depth. Within the upper 6 km of the Earth's crust the stress cating that plate boundary forces are the major control field is mapped by a wide range of methods with borehole breakouts as a major contributor. Below ~6 km depth focal mechanism solu- of the stress orientations and the tectonic regime. tions are the only stress indicators available, except a few deep sci- entific drilling projects. In order to avoid data that are mainly con- The World Stress Map project trolled by topography the minimum depth for stress data incorpo- rated in the WSM database is 100 m. The World Stress Map (WSM) was published in April 2007 by the Commission of the Geological Map of the World. It displays the Focal mechanism solutions tectonic regime and the orientation of the contemporary maximum horizontal compressional stress (SH) of more than 12,000 stress data The majority of stress data in the WSM database is derived records within the Earth's crust incorporating the WSM database from earthquake focal mechanism solutions (77%). The radiation release 2005 (Reinecker et al., 2005). The map is a Mercator projec- pattern of seismic wave from an earthquake allows us to construct a tion at 1:46,000,000 scale, including topography and bathymetry focal mechanism that consists of two perpendicular planes: the fault from Smith and Sandwell (1997) and plate boundary configuration plane and the auxiliary plane. They divide the volume into compres- from the global plate model PB2002 (Bird, 2003). sional and extensional quadrants. The orientation of these planes The goal of the WSM project is the development and compila- determine the orientation of the compressional (P), intermediate (B), tion of the extensive, quality-ranked stress database with a focus on and extensional (T) axes. These principal strain axes are used as determining the orientation of SH in the Earth's crust. However, the proxies for the orientation of the principal stresses axes 1, 2, and database also contains relative and absolute stress magnitudes and 3, but due to the uncertainties of this first-order approximation the additional information about each data point (such as depth, date, quality of the stress orientations derived from focal mechanism solu- reference of the original work). The initial phase of the WSM tions is restricted to C-quality data (i.e., a deviation of up to ±25° is project was within the International Lithosphere Program (ILP) from assumed). Furthermore, when a focal mechanism solution is located 1986–1992, led by Mary Lou Zoback in co-operation with more than in the vicinity of a plate boundary, and the kinematics of the focal 30 scientists worldwide. Since 1995, the WSM has been a project of mechanism solution is similar to the plate boundary kinematics, the the Heidelberg Academy of Sciences and Humanities, based at the event is omitted and flagged as a Possible Plate Boundary Event Geophysical Institute of University of Karlsruhe, Germany. The indicating that the P-, B-, and T-axis of the focal mechanism solution WSM is a public-domain project that provides all of its data, soft- might predominantly reflect the geometry and kinematics of the ware and additional services free of charge (available online at plate boundary, rather than the orientation of the regional stress field. www.world-stress-map.org). Stress orientation from a group of focal mechanism solutions (or The 2005 release of the WSM database contains 15,969 stress geologic fault-slip data), determined with stress inversion methods, data records with stress indicators interpreted from a range of meth- are also included in the database. ods within the upper 40 km of the lithosphere. The past WSM releases gave insight into large-scale patterns of Borehole breakouts regional stress orientations, i.e., the first-order stress patterns due to plate boundary forces, and second-order patterns due to topography, Borehole breakouts are stress-induced elongations of the well- large lateral density variations, and deglaciation effects (Zoback, bore cross-section and are formed when the circumferential stress 1992). However, in addition to further defining broad-scale stress concentration at the wellbore wall exceeds the stress required to patterns, the WSM 2005 database release has developed some cause compressive failure of the formation. The elongation of the regions of high data resolution that enable the user to investigate wellbore cross-section is the result of compressive shear failure on variations in stress orientations on local scales and to discuss factors intersecting conjugate planes. In vertical boreholes the maximum controlling third-order stress patterns such as active faults, local stress at the borehole wall occurs perpendicular to SH. Similar to inclusions, detachment horizons, and density contrasts. These forces these borehole breakouts drilling-induced tensile fractures are act as a major control on the stress field orientations when the mag- caused by tensile failure of the borehole wall and form when the nitudes of the horizontal stresses are close to isotropic (Heidbach et wellbore stress concentration is less than the tensile strength of the al., 2007; Tingay et al., 2005). rock. Drilling-induced tensile fractures form parallel to the SH orien- The database contains a wide range of stress indicators such as tation in vertical boreholes. Borehole breakouts are interpreted from hydraulic fracturing from which under ideal conditions the full stress oriented four- or six-arm caliper log data (e.g., the High-Resolution tensor can be determined and focal mechanism solutions that deliver Dipmeter Tool) or from acoustic or resistivity image logs (e.g., For- the orientation of the three principal stress axes and the tectonic mation Micro Imager, Simultaneous Acoustic and Resistivity regime, i.e., the relative magnitudes of SH, Sh (minimum horizontal Imager).

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In-situ stress measurements of the abbreviation given in the data record fields REF1-REF4 and in the format of the bibliography software Endnote®; (4) Visualization Hydraulic fracturing is analog to the drilling-induced tensile tool CASMI; (5) Website of the WSM that contains all information fractures, but here the fractures are artificially induced by pressurizing on the project and technical details of the database. an isolated section of a borehole until a tensile fracture occurs. Over- coring is a stress relief measurement that is quite common in mines and civil engineering projects. Here the deformation (elastic relaxation) of Discussion and conclusion a small rock specimen (a few cm3) is measured after its removal from The WSM project provides fundamental insights into the first- ambient rock. With the knowledge of the elastic rock properties the and second-order crustal stress pattern on plate-wide and regional stress tensor is derived. Both methods have the potential—under ideal scales larger than 500 km as well as on the forces controlling them. conditions—that the full stress tensor can be deduced. The SH orientation in North America, South America and Europe Geologic indicators are, at the plate-wide scale, predominately sub-parallel to absolute or relative plate motions. This correlation of SH orientation and plate The estimation of stress orientations from geological indicators motion suggests that the first-order intraplate stress patterns are the for the WSM database is restricted to young data, i.e., from Quaternary result of the same forces that drive plate motion, in particular ridge age. There is two major geological stress indicators: igneous dikes push, slab pull, trench suction, collisional forces, and traction at the and volcanic alignments and fault-slip analysis. Analog to the base of the lithosphere (Hillis and Reynolds, 2000; Müller et al., hydraulic fracture, igneous dikes and volcanic alignments grow in the 1992; Richardson, 1992; Zoback, 1992). Second-order stress patterns plane of the SH orientation. In the fault-slip analysis striae or slicken- at 100–500 km scales indicate that lateral density contrasts due to sides on fault planes are used. To receive a stable stress inversion for continental rifting, isostatic compensation and topography, deglacia- the principal stress orientations and their relative magnitudes, a tion effects, as well as lithospheric flexure have an additional impact sufficiently high number of slip directions from faults with different on regional-scale stress fields. orientations at a given local side is required (Sperner et al., 2003). Some regions of the map provide high data density that enables Quality-ranking of the data us to investigate third-order stress pattern and its sources at smaller scales due to active faults, local inclusions, detachment horizons, The success of the WSM is based on a standardized quality rank- and density contrasts. Some of these regions (e.g., northern ing scheme for the individual stress indicators making them compa- Germany) with high data density exhibit stress rotations with respect rable on a global scale. The quality ranking scheme was introduced to the plate-wide and regional stress orientation (Heidbach et al., by Zoback and Zoback (1991; 1989), and refined and extended by 2007; Tingay et al., 2006). Sperner et al. (2003). It is internationally accepted and guarantees reliability and global comparability of the stress data. Each stress data Perspectives of the WSM project record is assigned a quality between A and D, with A being the high- est quality and D the lowest. A-quality means that the SH orientation The progress in understanding the contemporary stress pattern is accurate to within ±15°, B-quality to within ±20°, C-quality to in the last two decades has only been possible due to the ongoing within ±25°, and D-quality to within ±40°. For most methods these systematic compilation of stress data with international collabora- quality classes are defined through standard deviation of SH. For tion. Even though the WSM project will end as a project of the example, an A-quality stress orientation estimate from borehole Heidelberg Academy of Sciences and Humanities by the end of breakouts requires the observation of at least 10 consistently oriented 2008, we will continue our work. From 2009 onwards, the project breakouts (with a standard deviation <12°) in a single borehole with will be maintained and further developed at the GeoForschungsZen- a total breakout length of over 300 m. Furthermore, the quality rank- trum (GFZ) Potsdam, Germany. However, the future success of the ing of all stress indicators facilitates the comparison of stress data WSM is nevertheless dependent on the assistance of the scientific determined from different methods and depths. In general, A, B, and community. We thus call for active participation in the further C quality stress indicators are considered reliable for use in analyzing development of the WSM database release regardless of which type stress patterns and the interpretation of geodynamic processes. of support: new stress data, the analysis of the stress field of a spe- The World Stress Map services cific region, or discussions on new stress determination methods. The website of the WSM project is equipped with the easy-to- Acknowledgements use database interface CASMO (Create A Stress Map Online) for the custom building of individual stress maps by simply selecting the The World Stress Map project is a collaborative project that region of interest, stress indicator type, depth range, and quality of would not be possible without the effort of many scientists world- the stress data (Heidbach et al., 2004). In addition, users can add wide. We are indebted to numerous individual researchers and their own stress data to this plot. The return time for a CASMO working groups all over the world for providing stress data. The request is less than a minute and the stress map is delivered via e- complete list of contributors is too numerous to be given herein. mail (Heidbach and Höhne, 2007). Alternatively the user can install However, the authors are particularly grateful for major contribu- the offline software CASMI (Create A Stress Map Interactively). tions for the WSM 2005 database release by Richard Hillis and Scott CASMI is a public domain program running under Unix-like operat- Reynolds of the Australasian Stress Map project (University of ing systems based on GMT (Wessel and Smith, 1995). It has a Adelaide), Lourdes Colmenares (Stanford University), Philip graphical user interface and specific features needed to visualize the Fleckenstein (Karlsruhe University), Mihaela Negut (PETROM, WSM data. CASMI includes the WSM 2005 database release and Bucarest), Paola Montone (INGV, Rome), Maria Teresa Mariucci will be sent free of charge after registration at the project's web site (INGV, Rome), Mark Zoback (Stanford University), and John (http://www.world-stress-map.org/casmi). Townend (University of Wellington). We also thank the World Stress Map advisory board members Egon Althaus, John Cook, Roy Digital data Gabrielsen, Domenico Giardini, Helmut Kipphan, Onno Oncken, The CD-ROM of the WSM has five sections: (1) Global stress Chris Reigber, Markus Rothacher, and Mark Zoback for the long- map in a layered pdf format; (2) WSM database release 2005 in three term support. We especially want to express our thanks to Jean-Paul different formats (*.xls, *.csv, *.dbf); (3) Bibliography of the WSM Cadet and Philippe Rossi from the Commission of the Geological 2005 database release with 1593 references. It is given in two for- Map of the World for the effort and enthusiasm they devoted to this mats: A raw text file with the references listed in alphabetical order project.

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References Relevant web site

Bird, P., 2003, An updated digital model for plate boundaries, Geochem- World Stress Map Project istry. Geophysics. Geosystems, v. 4, no. 34, art. no. 1027, doi:10.1029/ http://www.world-stress-map.org 2001GC000252. Heidbach, O., A. Barth, P. Connolly, F. Fuchs, B. Müller, J. Reinecker, B. Sperner, M. Tingay, and F. Wenzel, 2004, Stress Maps in a Minute: To order The 2004 World Stress Map Release, Eos Transactions, v. 85, pp. 521–529. World Stress Map Heidbach, O., and J. Höhne, 2007, CASMI— a tool for the visualization of the World Stress Map data base, Computers and Geosciences, in press. Mercator Projection Heidbach, O., J. Reinecker, M. Tingay, B. Müller, B. Sperner, K. Fuchs, Equatorial scale: 1 : 46,000,000 and F. Wenzel, 2007, Plate boundary forces are not enough: Second- Total surface of the map: 120 × 545 cm and third-order stress patterns highlighted in the World Stress Map © CCGM & Heidelberg Academy of Sciences and Humanities 2007 database, Tectonics, in press. Price: 15.00 Euros including CD-ROM Hillis, R.R., and S.D. Reynolds, 2000, The Australian Stress Map, Journal To order this map: www.ccgm.org - [email protected] Geological Society, v. 157, pp. 915–921. Müller, B., M.L. Zoback, K. Fuchs, L. Mastin, S. Gregersen, N. Pavoni, O. Stephansson, and C. Ljunggren, 1992, Regional Patterns of Tectonic Stress in Europe, Journal Geophysical Research, v. 97, pp. Oliver Heidbach 11783–11803. Geophysical Institute Reinecker, J., O. Heidbach, M. Tingay, B. Sperner, and B. Müller, 2005, Karlsruhe University The 2005 release of the World Stress Map (available online at Hertzstr. 16 www.world-stress-map.org). Richardson, R.M., 1992, Ridge Forces, Absolute Plate Motions, and the 76187 Karlsruhe Intraplate Stress Field, Journal Geophysical Research, v. 97, pp. Germany 11739–11748. Smith, W.H.F., and D.T. Sandwell, 1997, Global Sea Floor Topography Karl Fuchs, Birgit Müller & Friedemann Wenzel from Satellite Altimetry and Ship Depth Soundings, Science, v. 277, Geophysical Institute pp. 1956–1962. Karlsruhe University Sperner, B., B. Müller, O. Heidbach, D. Delvaux, J. Reinecker, and K. Hertzstr. 16 Fuchs, 2003, Tectonic stress in the Earth's crust: advances in the World 76187 Karlsruhe Stress Map project, in D.A. Nieuwland, ed., New insights in structural Germany interpretation and modelling, Special Publication Series, v. 212, Geo- logical Society, London, pp. 101–116. Heidelberg Academy of Sciences and Humanities Tingay, M., B. Müller, J. Reinecker, O. Heidbach, F. Wenzel, and Fleck- Karlst. 4 enstein.P., 2005, The World Stress Map Project 'Present-day Stress in 69117 Heidelberg Sedimentary Basins' initiative: building a valuable public resource to understand tectonic stress in the oil patch, The Leading Edge, v. 24, pp. Germany 1276–1282. Tingay, M.R.P., B. Müller, J. Reinecker, and O. Heidbach; 2006, State and John Reinecker Origin of the Present-day Stress Field in Sedimentary Basins: New Institute of Geosciences Results from the World Stress Map Project, 41st U.S. Symposium on University of Tübingen Rock Mechanics (USRMS): "50 Years of Rock Mechanics—Land- Sigwartstrasse 10, marks and Future Challenges.", Golden, Colorado, June 17–21, 2006, 72076 Tübingen pp. 1–14. Germany Wessel, P., and W.H.F. Smith, 1995, New version of Generic Mapping Tools Released, Eos Transactions, v. 76, p. 329. Mark Tingay Zoback, M.L., and M.D. Zoback, 1989, Tectonic stress field of the conter- School of Earth & Environmental Sciences minous United States, in L.C. Pakiser and W.D. Mooney, eds., Geo- DP313 Mawson Building physical Framework of the Continental United States, v. 172, Geolog- University of Adelaide SA 5005 ical Society America Memoir, Boulder, Colorado, pp. 523–539. Australia Zoback, M.D., and M.L. Zoback, 1991, Tectonic stress field of North America and relative plate motions, in D.B. Slemmons, E.R. Engdahl, M.D. Zoback´, and D.D. Blackwell, eds., Neotectonics of North Amer- Blanka Sperner ica, Decade Map, v. I, Geological Society of America, Boulder, Col- Geological Institute orado, pp. 339–366. TU Bergakademie Freiberg Zoback, M.L. 1992, First and second order patterns of stress in the litho- Bernhard-von-Cotta-Str. 2 sphere: The World Stress Map Project, Journal of Geophysical 09599 Freiberg Research, v. 97, no. B8, pp. 11703–11728. Germany

Episodes, Vol. 30, no. 3 180° 210° 240° 270° 300° 330° 0° 30° 60° 90° 120° 150° 180° Commission de la Carte Géologique du Monde / Commission for the Geological Map of the World Major contributors n=8582 Australasian Stress Map Project, Harvard CMT Catalogue, European-Mediterranean Regional CMT solutions, DGMK, WEG, NAGRA, PETROM BP, Schlumberger, CHEVRON-Texaco, WORLD STRESS MAP Fennoscandian Rock Stress Database, A project of the Heidelberg Academy of Sciences and Humanities Wintershall, Shell, Karasu, PTT, Eni, RWE-Dea, Daleel Petroleum WSM Release 2005 - www.world-stress-map.org Adams, J. Klein, R. Al-Zoubi, A.S. Kjorholt, H. Editors: Heidbach, O., Fuchs, K., Müller, B., Reinecker, J., Sperner, B., Tingay, M., Wenzel, F. Ask, M. Knoll, P. Assumpçaõ, M. Kropotkin, P. Batchelor, T. Larsen, R. Becker, A. Lindholm, C. Bell, S. López, A. Bergerat, F. Magee, M. Bergman, E. Mariucci, M.T. Explanatory Text Barr, M. Mastin, M. The World Stress Map (WSM) is the global compilation of All tectonic stress information is recorded in a standardized Bluemling, P. Maury, V. information on the present-day tectonic stress field in the format and quality-ranked for reliability and comparability on Bonjer, K.-P. Mercier, J. Earth's crust. The WSM is a collaborative project between a global scale. The stress maps on this poster display A-C Bosworth, W. Mildren, S. academia, industry and government that aims to understand quality intraplate stress data in the upper 40 km of the Bratli, R. Montone, P. the origin and factors controlling stresses in the lithosphere. lithosphere from the WSM 2005 database release. Brereton, R. Müller, B. The project commenced in 1986 as a part of the International Single-event focal mechanism solutions determined as Brudy, M. Negut, M. 60° Lithosphere Program, under the leadership of Mary Lou being potentially spurious (labeled as 'Possible Plate 60° Colmenares, L. Oncescu, M.C. Zoback. Since 1995, the WSM has been a project of the Boundary' events in the database) are not displayed. Connolly, P. Pavoni, N. Heidelberg Academy of Sciences and Humanities, and is Further detailed information on the project can be found on Cornet, F. Ragg, S. located at the Geophysical Institute of Karlsruhe University. the WSM website at www.world-stress-map.org. Deichmann, N. Rajendran, K. Delvaux, D. Reinecker, J. Denham, D. Reynolds, S.D. Doeveny, P. Roth, F. The stress maps display the maximum horizontal compressional stress SH Enever, J. Rummel, F. Feijerskov, M. Sebrier, M. Method Quality Stress Regime Finkbeiner, T. Sherman, S. Fleckenstein, P. Stephansson, O. focal mechanism A SH is within ± 15° Normal faulting Gay, N. Stromeyer, D. Gerner, P. Sperner, B. breakouts B SH is within ± 20° Strike-slip faulting Gough, D.I. Suarez, G. Thrust faulting drill. induced frac. C SH is within ± 25° Gowd, T.N. Suter, M. Unknown regime Grasso, M. Tingay, M. overcoring Gregersen, S. Tolppanen, P. S S S Grünthal, G. Townsend, J. V V V hydro. fractures Gupta, H.K. Udias, A. geol. indicators Gvishiani, A. van Dalfsen, W. S S h Haimson, B.C. van Eijs, R. H S h SH S S NF h H Hanssen, T.H. Van-Kin, L. SS TF Heidbach, O. Wiprut, D. Data depth range Hickman, S. Wolter, K. 0-40 km normal faulting regime strike-slip regime thrust faulting regime Hillis, R.R. Yunga, S. S > S > S Horvath, F. Zhonghuai, X. v H h SH > Sv > Sh SH > Sh > Sv Jarosinski, M. Zoback, M.D. Jianmin, D. Zoback, M.L. 30° 30° Jurado, M.J. 350° 0° 10° 20° 30° 60° 60°

n=1969 Advisory board of the WSM project Egon Althaus, Karlsruhe University John Cook, Schlumberger, Cambridge Roy H. Gabrielsen, University of Bergen Domenico Giardini, ETH Zürich Helmut Kipphan, Heidelberger Druckmaschinen, Heidelberg Onno Oncken, GeoForschungsZentrum Potsdam Christoph Reigber, GeoForschungsZentrum Potsdam 55° 55° Markus Rothacher, GeoForschungsZentrum Potsdam Mark D. Zoback, Stanford University, California

Further information and data access All stress data, further information and software tools are available free of charge on the project website at: www.world-stress-map.org

0° 0° 50° 50° Citation of this map Heidbach, O., Fuchs, K., Müller, B., Reinecker, J., Sperner, B., Tingay, M., Wenzel, F. (eds.), The World Stress Map - Release 2005, Commission for the Geological Map of the World, Paris, 2007.

References of used data and software 45° 45° This map made use of a number of datasets: Plate boundaries are from the global plate model PB2002 (Bird, 2003), topography and bathymetry from Smith and Sandwell (1997). Stress maps are produced with CASMI (Heidbach and Höhne, in press) which is based on GMT from Wessel and Smith (1998). Bird, P., An updated digital model for plate boundaries, Geochem. Geophys. Geosyst., 4 (3), 1027, doi:10.1029/ 40° 40° 2001GC000252, 2003. Heidbach, O., and Höhne, J., CASMI - a tool for the visualization of the World Stress Map database, Computers & Geosciences, in press. -30° -30° Wessel, P., and Smith, W.H.F., New, improved version of Generic Mapping Tools released, Eos Trans., 79 (47), 579, 35° 35° 1998. Smith, W.H.F., and Sandwell, D.T., Global sea floor topography 350° 0° 10° 20° 30° from satellite altimetry and ship depth soundings, Science, 277, 1956-1962, 1997. 230° 240° 250° 260° 50° 50°

Key references for the WSM project Fuchs, K., and Müller, B., World Stress Map of the Earth: a key to tectonic processes and technological applications, Naturwissenschaften, 88, 357-371, 2001. Heidbach, O., Barth, A., Connolly, P., Fuchs, K., Müller, B., Reinecker, J., Sperner, B., Tingay, B., and Wenzel, F., Stress maps in a minute: The 2004 World Stress Map Release, Eos Trans., 85 (49), 521-529, 2004. 45° 45° Sperner, B., B. Müller, O. Heidbach, D. Delvaux, J. Reinecker, and K. Fuchs, Tectonic stress in the Earth's crust: advances in the World Stress Map project, in: New insights in structural interpretation and modelling, Geol. Soc. Spec. Pub, 212, edited by D.A. Nieuwland, pp. 101-116, Geological Society, London, 2003. Tingay, M., Müller, B., Reinecker, J., Heidbach, O., Wenzel, F., and Fleckenstein, P., The World Stress Map Project n=551 'Present-day Stress in Sedimentary Basins' initiative: 40° 40° building a valuable public resource to understand tectonic stress in the oil patch, The Leading Edge, 24 (12), -60° -60° 1276-1282, 2005. Zoback, M.L., First and second order patterns of stress in the lithosphere: The World Stress Map Project, J. Geophys. Res., 97, 11703-11728, 1992. Zoback, M.D., and Zoback, M.L.,Tectonic stress field of North America and relative plate motions, in: Neotectonics of North America Decade Map Volume I, edited by 35° 35° Slemmons, D.B., Engdahl, E.R., Zoback, M.D., and Blackwell, D.D., pp. 339-366, Geol. Soc. Am., Boulder, Colorado, 1991. Zoback, M.L., and Zoback, M.D., Tectonic stress field of the inset area conterminous United States, in: Geophysical Framework of the Continental United States, edited by Pakiser, L.C., and Mooney, W.D., pp. 523-539, Geol. Soc. Am. Mem. 172, n=1029 Projection is Mercator, scale at Equator is 1:46 M Boulder, Colorado, 1989. 30° 30° 230° 240° 250° 260° 180° 210° 240° 270° 300° 330° 0° 30° 60° 90° 120° 150° 180°