Plate boundary forces are not enough: Second‐ and third‐order stress patterns highlighted in the World Stress Map database

Abstract

The World Stress Map Project compiles a global database of contemporary tectonic stress information of the Earth's crust. Early releases of the World Stress Map Project demonstrated the existence of first‐order (plate‐scale) stress fields controlled by plate boundary forces and second‐order (regional) stress fields controlled by major intraplate stress sources such as mountain belts and zones of widespread glacial rebound. The 2005 release of the World Stress Map Project database provides, for some areas, high data density that enables us to investigate third‐order (local) stress field variations, and the forces controlling them such as active faults, local inclusions, detachment horizons, and density contrasts. These forces act as major controls on the stress field orientations when the magnitudes of the horizontal stresses are close to isotropic. We present and discuss examples for Venezuela, Australia, Romania, Brunei, western Europe, and southern Italy where a substantial increase of data records demonstrates some of the additional factors controlling regional and local stress patterns.

3-D geomechanical–numerical model of the contemporary crustal stress state in the Alberta Basin (Canada)

“…This would allow large stress rotation due to small local stress sources (Heidbach et al, 2007). However, from the provided data, this explanation can be ruled out, and the previously stated explanation is much more likely.…”

“…A similar change from surface to depth is observed: from thrust faulting at < 350-600 m in depth, strike slip in a depth range of about 500-2500 m, down to normal faulting at greater depths > 2500 m (Bell and Babcock, 1986;Fordjor et al, 1983;Jenkins and Kirkpatrick, 1979). There is also a varying S hmin gradient discussed (Bachu et al, 2008;Bell and Grasby, 2012;Hawkes et al, 2005), but this is may be due to different measurement methods (Bell et al, 1994) or man-made stress changes. The S Hmax /S hmin ratio in the Alberta Basin is about 1.3-1.6 .…”

“…The stress pattern is driven and altered by several stress sources; they are discriminated depending on the scales into first-order (> 500 km), second-order (100-500 km) and third-order stress sources (< 100 km) (Heidbach et al, 2007Müller et al, 1997;Tingay et al, 2005;Zoback, 1992;Zoback and Mooney, 2003). First-order stress sources as the main driving forces are summarized as plate boundary forces, which are ridge push, slab pull, and trench suction, gravity and basal drag by mantle convection.…”

The seismotectonics of western Skagerrak

“…The presented investigation of the Skagerrak seismicity confirms that the regional stress field is dominated by ridge push forces from the mid-Atlantic ridge, moderated locally (Gregersen 1992;Hicks et al 2000;Heidbach et al 2007;Bungum et al 2009) by other stress sources and geological structure weaknesses.…”

Lithospheric Stress Tensor from Gravity and Lithospheric Structure Models

“…Among existing studies we could mention earlier works by Richardson et al (1979), Richardson (1992), and Bai et al (1992), or more recent studies by Steinberger et al (2001), Lithgow-Bertelloni and Guynn (2004), and Naliboff et al (2009, 2012. Furthermore, bore-hole breakouts, hydraulic fracturing, volcanic alignment, seismic focal mechanisms, heat flow on faults, transform fault azimuths, and other in situ stress measurements were also used to investigate and predict the global stress pattern (Zoback and Zoback 1991;Sperner et al 2003;Heidbach et al 2007Heidbach et al , 2010 and to compile the World Stress Map Database (Zoback 1992;Heidbach et al 2016).…”