Hans Wason | Indian Institute Of Technology, Roorkee (original) (raw)
Papers by Hans Wason
Bulletin of the Seismological Society of America, 2014
For regression of variables having measurement errors, general orthogonal regression (GOR) is the... more For regression of variables having measurement errors, general orthogonal regression (GOR) is the most appropriate statistical procedure that yields a linear relation between the true values of the dependent (y t) and independent (x t) variables. However, the GOR procedure to obtain unbiased estimate of the dependent variable for a given error-affected value of the predictor variable is not well addressed in the literature. In the conventional GOR approach, the error-affected value of the predictor variable is substituted as such in the GOR relation, yielding biased estimates of y t. In another approach, the orthogonal projections of the given points on the GOR line are used to first estimate x t and then y t. In this study, a procedure making use of true points on the GOR line is proposed to obtain improved estimates of y t. The proposed GOR procedure is applied to the magnitude conversion problem between m b to M w and M s to M w , using real data set. The absolute average differences of the estimates obtained and their standard deviations are compared, indicating that the proposed GOR procedure provides improved estimates of the dependent variable (y t) compared with the conventional GOR approach. The improved unified magnitudes obtained using the proposed GOR procedure will result in more realistic seismic hazard for a given catalog and seismotectonic environment.
Geophysical Journal International, 2014
ABSTRACT The argument proposed by Wason et al. that the conversion of magnitudes from a scale (e.... more ABSTRACT The argument proposed by Wason et al. that the conversion of magnitudes from a scale (e.g. Ms or mb) to another (e.g. Mw), using the coefficients computed by the general orthogonal regression method (Fuller) is biased if the observed values of the predictor (independent) variable are used in the equation as well as the methodology they suggest to estimate the supposedly true values of the predictor variable are wrong for a number of theoretical and empirical reasons. Hence, we advise against the use of such methodology for magnitude conversions.
Journal of Earth System …, 2003
Damage observed during the Kutch earthquake of 26th January 2001 is classified according to the t... more Damage observed during the Kutch earthquake of 26th January 2001 is classified according to the type of structure. This damage pattern has been used to draw the isoseismal map on the basis of the intensity scale given in IS 1893-2002 which covers only traditional one to two storey houses. Having thus estimated intensities, and observed damage to other types of structures, a new criterion was adopted which is included in this paper. Areas that showed maximum damage to structures have been assigned maximum intensity X.
Bulletin of the Seismological Society of America
An addition theorem for spherical waves is used to transform the displacement field due to an arb... more An addition theorem for spherical waves is used to transform the displacement field due to an arbitrary shear dislocation in an unbounded homogeneous medium with origin at the focus to that in a coordinate system with origin at the center of the Earth. The final results are expressed in terms of the eigenvector solutions of the vector Naviér equation of dynamical elasticity. Some serious mistakes in recent papers on the subject have been pointed out.
Journal of Earth System Science
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
A strong earthquake with magnitude M w 7.7 that shook the Indian Province of Gujarat on the morni... more A strong earthquake with magnitude M w 7.7 that shook the Indian Province of Gujarat on the morning of January 26, 2001, caused widespread appearance of water bodies and channels, in the Rann of Kachchh and the coastal areas of Kandla port. In this work, the impact of using conventional band ratio indices from Landsat-7 temporal images for liquefaction extraction was empirically investigated and compared with Class Based Sensor Independent (CBSI) spectral band ratio while applying noise classifier as soft computing approach via supervised classification. Five spectral indices namely, SR (Simple Ratio), NDVI (Normalized Difference Vegetation index), TNDVI (Transformed Normalized Difference Vegetation Index), SAVI (Soil-Adjusted Vegetation Index) and Modified Normalized Difference Water Index (MNDWI) were investigated to identify liquefaction using temporal multi-spectral images. It is found that CBSI-TNDVI with temporal data has higher membership range (0.968-0.996) and minimum entropy (0.011) to outperform for extraction of liquefaction and for water bodies extraction membership range (0.960-0.996) and entropy (0.005) respectively.
Physics of the Earth and Planetary Interiors
The digital seismic data recorded by a telemetered seismic array has been used to compute seismic... more The digital seismic data recorded by a telemetered seismic array has been used to compute seismic moments and stress drops of local earthquakes in the Garhwal Himalaya region based on Brune's model of the earthquake source. The seismic moments for 18 shallow focus earthquakes range from 7 x 1018 dyn cm to 6.23 X 1021 dyn cm. These earthquakes are found to have very low stress drops; less than 1 bar for seven events and between 1 bar and 10 bars for another seven events. The maximum stress drop is found to be 38 bars for an earthquake of magnitude 4.2 with focal depth 15 km. The shallow focus events having low stress drops in this region indicate that the crust has low strength to withstand the accumulated strain energy.
Major seismic activity in India is concentrated along the Himalayan arc including the western Him... more Major seismic activity in India is concentrated along the Himalayan arc including the western Himalaya. A region in the vicinity of Main Boundary Thrust (MBT) and Main Central Thrust (MCT) bounded by latitude 29o N to 36o N and longitude 73o E to 80o E was considered for the study. Nine Seismogenic Source Zones (SSZ), were identified on the basis of seismicity and the tectonics around it. Seismic hazard parameters were computed for each source zone and return periods were calculated for different magnitude earthquakes. For validation of return periods, seven recent earthquakes were studied. Out of seven earthquakes three earthquakes of magnitude between 5.0 and 6.0 occurred in Kangra SSZ . Two Ground Motion Prediction Equations (GMPE's) were used to estimate peak ground acceleration (PGA) in the region. PGA in the region was estimated to vary between 0.013 g to 0.315 g for 10% probability of exceedance in 50 years, and between 0.024 g to 0.68 g for 2% probability of exceedance in 50 years. Highest PGA values ≥ 0.31 g were observed in Kangra and Chamba district of Himachal Pradesh. For the Kangra SSZ, a return period of 141 years was estimated for magnitude Mw = 8.0, 44 years for Mw = 7 and 14 years for Mw = 6. Results obtained in the present study were compared with other studies. This hazard analysis study underlines the urgency for carrying out vulnerability analysis to estimate the populations that are at risk to this threat perception, so that appropriate mitigation measures can be put in place.
The difficult mountainous terrain, with poor accessibility, of the earthquake affected region cov... more The difficult mountainous terrain, with poor accessibility, of the earthquake affected region covering parts of Pakistan and India has become a natural hindrance for any comprehensive ground survey after Kashmir earthquake (8Th Oct, 2005). The capability to undertake earthquake damage identification and assessment can be improved through current advances in Remote Sensing technologies. This work is an attempt to document and identify urban damaged areas by spectral indices using temporal multi-spectral images from IRS-P6 LISS-IV images. In this work, Normalized Difference Vegetation Index (NDVI) using Possibilistic c Means (PCM) classifier has been applied as soft computing approach via supervised classification.
Bulletin of the Seismological Society of America, 2014
For regression of variables having measurement errors, general orthogonal regression (GOR) is the... more For regression of variables having measurement errors, general orthogonal regression (GOR) is the most appropriate statistical procedure that yields a linear relation between the true values of the dependent (y t) and independent (x t) variables. However, the GOR procedure to obtain unbiased estimate of the dependent variable for a given error-affected value of the predictor variable is not well addressed in the literature. In the conventional GOR approach, the error-affected value of the predictor variable is substituted as such in the GOR relation, yielding biased estimates of y t. In another approach, the orthogonal projections of the given points on the GOR line are used to first estimate x t and then y t. In this study, a procedure making use of true points on the GOR line is proposed to obtain improved estimates of y t. The proposed GOR procedure is applied to the magnitude conversion problem between m b to M w and M s to M w , using real data set. The absolute average differences of the estimates obtained and their standard deviations are compared, indicating that the proposed GOR procedure provides improved estimates of the dependent variable (y t) compared with the conventional GOR approach. The improved unified magnitudes obtained using the proposed GOR procedure will result in more realistic seismic hazard for a given catalog and seismotectonic environment.
Geophysical Journal International, 2014
ABSTRACT The argument proposed by Wason et al. that the conversion of magnitudes from a scale (e.... more ABSTRACT The argument proposed by Wason et al. that the conversion of magnitudes from a scale (e.g. Ms or mb) to another (e.g. Mw), using the coefficients computed by the general orthogonal regression method (Fuller) is biased if the observed values of the predictor (independent) variable are used in the equation as well as the methodology they suggest to estimate the supposedly true values of the predictor variable are wrong for a number of theoretical and empirical reasons. Hence, we advise against the use of such methodology for magnitude conversions.
Journal of Earth System …, 2003
Damage observed during the Kutch earthquake of 26th January 2001 is classified according to the t... more Damage observed during the Kutch earthquake of 26th January 2001 is classified according to the type of structure. This damage pattern has been used to draw the isoseismal map on the basis of the intensity scale given in IS 1893-2002 which covers only traditional one to two storey houses. Having thus estimated intensities, and observed damage to other types of structures, a new criterion was adopted which is included in this paper. Areas that showed maximum damage to structures have been assigned maximum intensity X.
Bulletin of the Seismological Society of America
An addition theorem for spherical waves is used to transform the displacement field due to an arb... more An addition theorem for spherical waves is used to transform the displacement field due to an arbitrary shear dislocation in an unbounded homogeneous medium with origin at the focus to that in a coordinate system with origin at the center of the Earth. The final results are expressed in terms of the eigenvector solutions of the vector Naviér equation of dynamical elasticity. Some serious mistakes in recent papers on the subject have been pointed out.
Journal of Earth System Science
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
A strong earthquake with magnitude M w 7.7 that shook the Indian Province of Gujarat on the morni... more A strong earthquake with magnitude M w 7.7 that shook the Indian Province of Gujarat on the morning of January 26, 2001, caused widespread appearance of water bodies and channels, in the Rann of Kachchh and the coastal areas of Kandla port. In this work, the impact of using conventional band ratio indices from Landsat-7 temporal images for liquefaction extraction was empirically investigated and compared with Class Based Sensor Independent (CBSI) spectral band ratio while applying noise classifier as soft computing approach via supervised classification. Five spectral indices namely, SR (Simple Ratio), NDVI (Normalized Difference Vegetation index), TNDVI (Transformed Normalized Difference Vegetation Index), SAVI (Soil-Adjusted Vegetation Index) and Modified Normalized Difference Water Index (MNDWI) were investigated to identify liquefaction using temporal multi-spectral images. It is found that CBSI-TNDVI with temporal data has higher membership range (0.968-0.996) and minimum entropy (0.011) to outperform for extraction of liquefaction and for water bodies extraction membership range (0.960-0.996) and entropy (0.005) respectively.
Physics of the Earth and Planetary Interiors
The digital seismic data recorded by a telemetered seismic array has been used to compute seismic... more The digital seismic data recorded by a telemetered seismic array has been used to compute seismic moments and stress drops of local earthquakes in the Garhwal Himalaya region based on Brune's model of the earthquake source. The seismic moments for 18 shallow focus earthquakes range from 7 x 1018 dyn cm to 6.23 X 1021 dyn cm. These earthquakes are found to have very low stress drops; less than 1 bar for seven events and between 1 bar and 10 bars for another seven events. The maximum stress drop is found to be 38 bars for an earthquake of magnitude 4.2 with focal depth 15 km. The shallow focus events having low stress drops in this region indicate that the crust has low strength to withstand the accumulated strain energy.
Major seismic activity in India is concentrated along the Himalayan arc including the western Him... more Major seismic activity in India is concentrated along the Himalayan arc including the western Himalaya. A region in the vicinity of Main Boundary Thrust (MBT) and Main Central Thrust (MCT) bounded by latitude 29o N to 36o N and longitude 73o E to 80o E was considered for the study. Nine Seismogenic Source Zones (SSZ), were identified on the basis of seismicity and the tectonics around it. Seismic hazard parameters were computed for each source zone and return periods were calculated for different magnitude earthquakes. For validation of return periods, seven recent earthquakes were studied. Out of seven earthquakes three earthquakes of magnitude between 5.0 and 6.0 occurred in Kangra SSZ . Two Ground Motion Prediction Equations (GMPE's) were used to estimate peak ground acceleration (PGA) in the region. PGA in the region was estimated to vary between 0.013 g to 0.315 g for 10% probability of exceedance in 50 years, and between 0.024 g to 0.68 g for 2% probability of exceedance in 50 years. Highest PGA values ≥ 0.31 g were observed in Kangra and Chamba district of Himachal Pradesh. For the Kangra SSZ, a return period of 141 years was estimated for magnitude Mw = 8.0, 44 years for Mw = 7 and 14 years for Mw = 6. Results obtained in the present study were compared with other studies. This hazard analysis study underlines the urgency for carrying out vulnerability analysis to estimate the populations that are at risk to this threat perception, so that appropriate mitigation measures can be put in place.
The difficult mountainous terrain, with poor accessibility, of the earthquake affected region cov... more The difficult mountainous terrain, with poor accessibility, of the earthquake affected region covering parts of Pakistan and India has become a natural hindrance for any comprehensive ground survey after Kashmir earthquake (8Th Oct, 2005). The capability to undertake earthquake damage identification and assessment can be improved through current advances in Remote Sensing technologies. This work is an attempt to document and identify urban damaged areas by spectral indices using temporal multi-spectral images from IRS-P6 LISS-IV images. In this work, Normalized Difference Vegetation Index (NDVI) using Possibilistic c Means (PCM) classifier has been applied as soft computing approach via supervised classification.