Abstract-The standard data fusion methods may not be satisfactory to merge a high-resolution panchromatic image and a low-resolution multispectral image because they can distort the spectral characteristics of the multispectral data. In this paper, we developed a technique, based on multiresolution wavelet decomposition, for the merging and data fusion of such images. The method presented here consists of adding the wavelet coefficients of the high-resolution image to the multispectral (lowresolution) data. We have studied several possibilities concluding that the method which produces the best results consists in adding the high order coefficients of the wavelet transform of the panchromatic image to the intensity component (defined as L = R+G+B 3 ) of the multispectral image. The method is, thus, an improvement on standard intensity-hue-saturation (IHS or LHS) mergers. We used the "à trous" algorithm which allows to use a dyadic wavelet to merge nondyadic data in a simple and efficient scheme. We used the method to merge SPOT and LANDSAT (TM) images. The technique presented is clearly better than the IHS and LHS mergers in preserving both spectral and spatial information.

The analysis of seismic signals obtained from near‐source triaxial accelerometer recordings of two sets of single‐block rockfall experiments is presented. The tests were carried out under controlled conditions in two quarries in northeastern Spain; in the first test (Foj limestone quarry, Barcelona), 30 blocks were released with masses ranging between 475 and 11,480 kg. The second test (Ponderosa andesite quarry, Tarragona) consisted of the release of 44 blocks with masses from 466 to 13,581 kg. An accelerometer and three high‐speed video cameras were deployed, so that the trajectories, velocities, and block fragmentation could be tracked precisely. These data were used to explore the relationship between seismic energy and rockfall kinetics (the latter obtained from video analysis). We determined absolute and relative values of seismic energy and used them to estimate rockfall volumes. Finally, the seismic signature of block fragmentation was assessed in both the frequency and time domains. The ratios of seismic energy after impact to kinetic energy before impact ranged between 10−7 and 10−4. These variables were weakly correlated. The use of seismic energy relative to impacting kinetic energy was preferred for the estimation of volumes. Block fragmentation impacts were dominated by higher acceleration spectrum centroid frequencies than those of nonfragmentation impacts: 56.62 ± 2.88 and 48.46 ± 4.39 Hz at Foj and 52.84 ± 12.73 and 38.14 ± 4.73 Hz at Ponderosa.

ABSTRACT:A Rockfall is a mass instability event frequently observed in road cuts, open pit mines and quarries, steep slopes and cliffs. After its detachment, the rock mass may disaggregate and break due to the impact with the ground surface, thus producing new rock fragments. The consideration of the fragmentation of the rockfall mass is critical for the calculation of the trajectories of the blocks and the impact energies, for the assessment of the potential damage and the design of protective structures. In this paper, we present RockGIS, a GIS-Based tool that simulates stochastically the fragmentation of the rockfall, based on a lumped mass approach. In RockGIS, the fragmentation is triggered by the disaggregation of the detached rock mass through the pre-existing discontinuities just before the impact with the ground. An energy threshold is defined in order to determine whether the impacting blocks break or not. The distribution of the initial mass between a set of newly generated rock fragments is carried out stochastically following a power law. The trajectories of the new rock fragments are distributed within a cone. The fragmentation model has been calibrated and tested with a 10,000m 3 rockfall that took place in 2011 near Vilanova de Banat, Eastern Pyrenees, Spain.

In this paper, we present the upgraded version of RockGIS, a stochastic program for the numerical simulation of rockfalls and their fragmentation, based on a fractal model. The code has been improved to account for a range of fragmentation scenarios, depending on the impact conditions. In the simulation, the parameters of the fractal fragmentation model that define the sizes of the generated fragments were computed at each impact according to the kinematic conditions. The performance of the upgraded code was verified and validated by real-scale rockfall tests performed in a quarry. The tests consisted of the release of 21 limestone blocks. For each release, the size and spatial distribution of the fragments generated by the impacts were measured by hand and from orthophotos taken via drone flights. The trajectories of the blocks and the resulting fragments were simulated with the code and calibrated with both the volume distribution and the runout distances of the fragments. Finally, as all the relevant rockfall parameters involved were affected by strong uncertainty and spatial variability, a parametric analysis was carried out and is discussed.

Real-scale fragmentation tests provide high quality data in order to study the fragmentation pattern of rock blocks. In the tests carried out, the initial rock mass, in terms of both volume and shape, was reconstructed by means of 3D photogrammetry. The fragments size distribution of the bocks tested was measured by hand using a tape. The drop tests were performed in four different sites, releasing a total of 124 blocks and measuring 2907 fragments. The obtained fragment size distributions may be well fitted using power laws. The survival rate (Sr), which is the proportion of remaining block shows a wide range of values. Observing the fragment distribution, two parameters are needed to characterize the fragmentation: the number of fragments produced and Sr. The intensity of the fragmentation is expressed by the exponent of the fitted power laws. Although the results are highly variable and show a stochastic behavior of the fragmentation, we have identified different patterns that reflect some local test conditions.