Two fixed-threshold (CCRS and ESA) and three contextual (GIGLIO, IGBP, and MODIS) algorithms were used for fire detection with Advanced Very High Resolution Radiometer (AVHRR) data acquired over Canada during the 1995 fire season. The CCRS algorithm was developed for the boreal ecosystem, while the other four are for global application. The MODIS algorithm, although developed specifically for use with the MODIS sensor data, was applied to AVHRR in this study for comparative purposes. Fire detection accuracy assessment for the algorithms was based on comparisons with available 1995 burned area ground survey maps covering five Canadian provinces. Overall accuracy estimations in terms of omission (CCRS=46%, ESA=81%, GIGLIO=75%, IGBP=51%, MODIS=81%) and commission (CCRS=0.35%, ESA=0.08%, GIGLIO=0.56%, IGBP=0.75%, MODIS=0.08%) errors over forested areas revealed large differences in performance between the algorithms, with no relevance to type (fixed-threshold or contextual). CCRS performed best in detecting real forest fires, with the least omission error, while ESA and MODIS produced the highest omission error, probably because of their relatively high threshold values designed for global application. The commission error values appear small because the area of pixels falsely identified by each algorithm was expressed as a ratio of the vast unburned forest area. More detailed study shows that most commission errors in all the algorithms were incurred in non-forest agricultural areas, especially on days with very high surface temperatures. The advantage of the high thresholds in ESA and MODIS was that they incurred the least commission errors. The poor performance of the algorithms (in terms of omission errors) is not only due to their quality but also to cloud cover, low satellite overpass frequency, and the saturation of AVHRR channel 3 at about 321 K. Great improvement in global fire detection can probably be achieved by exploring the use of a wide variety of channel combinations from the data-rich MODIS instruments. More sophisticated algorithms should be designed to accomplish this.

Multi-offset vertical-seismic-profiling (VSP) techniqueswere employed in the JAPEX/JNOC/GSC et al. Mallik 3L-38 observation well to image the gas hydrate zones in the immediate vicinity of the Mallik 5L-38 gas hydrate production research well. Conventional vertical-seismic-profiling - common-depth-point (VSP-CDP) transforms of the reflected wave field and resonance-scattering analysis from three-component VSP data provide information about lateral distribution of the gas hydrate and the internal structure of the gas hydrate zone. Compressional-wave velocities beneath the permafrost and within the gas hydrate zone averaged 2040 m/s and 2470 m/s, respectively. Within the gas hydrate zone, shear-wave velocities averaged 1100 m/s. At the Mallik well site, the gas hydrate zone is characterized by strong perturbations in compressional-wave velocities. The resonance-scattering analysis and full wave-form sonic logs from the JAPEX/JNOC/GSC Mallik 2L-38 and JAPEX/JNOC/GSC et al. Mallik 5L-38 wells indicate that important lateral variations in gas hydrate distribution must exist near the top of the gas hydrate zone, at about 900 m depth.