D. S. Subrahmanyam

In the Geological studies there are several field maps that are available to know the ground features and various geological parameters, but if the tectonic stress directions are measured at various available places and marked globally on a world map then it is called World Stress Map (WSM). These stress directions are helpful not only for academic research but also for compiling the vast data on a global scale to know the geodynamics and plate movement. The world stress map shows the orientations of Maximum Principal Horizontal Stress Direction measured at various places in different countries. There are two types of stresses available based on the regional and local scales. Regional stresses are also called first order estimates which are based on the measurements of earth quake focal mechanism studies at the particular site globally or regionally. But the second order stresses are completely local parameters generally carried out for specific engineering purpose. To prepare the world stress map the first order stresses are very important and generally incorporated in the world stress map and the less importance is given for second order stress, since these measurements are most of the times determined at shallow depths and are not reliable indicators to include in the stress map. However the first and second order stress directions are mapped on the world stress map to know the possible global phenomenon like plate dynamics. The world stress map is being prepared and updated periodically by WSM project. The 1992 version of the World Stress Map was derived mainly from geological observations on earthquake focal mechanisms, volcanic alignments and fault slip interpretations. Less than 5% of the data was based upon hydraulic fracturing or overcoring measurements of the type commonly used in mining and civil engineering projects. The 2005 version of world stress map shows the huge number of data collected from hydrofracturing, overcoring, borehole breakout etc.