We propose a modified centroid method to compute the depth to the bottom of magnetic sources (DBMS) based on a fractal source distribution. This approach provides better estimates than the assumption of an uncorrelated source distribution. We apply our approach to a recently compiled homogeneous set of aeromagnetic data from Germany. The deepest DBMS values are found for some large basin areas, i.e., the Molasse basin and parts of the North German basin. Smaller DBMS were estimated for the Moldanubian region in southern Germany and the northern part of the North German basin. A comparison of DBMS with heat-flow data, crustal temperatures at 3-km depths, and Moho depth indicates that DBMS is controlled by the geothermal condition of the earth’s crust in Germany and lithologic changes. Although the Upper Rhine graben and the Moldanubian region are characterized by small DBMS, a change in DBMS values in northern Germany seems to be related to the Elbe lineament.

We report GPS measurements of postseismic deformation from 22 campaign‐mode and one continuous GPS sites in the Andaman‐Nicobar region following the great Sumatra‐Andaman earthquake of 26 December 2004. Large horizontal displacements toward west to southwest, varying in magnitude from 10 to 40 cm, and with uplift reaching 16 cm, occurred in the region in the first year after the earthquake. The observed motion decreased logarithmically in the subsequent year. We suggest that in the Andaman region, frictional afterslip occurred farther downdip of the coseismic rupture, while in the Little Andaman and Nicobar regions, the coseismic rupture and afterslip patch partly overlapped. The afterslip was mostly aseismic and did not contribute to the aftershocks. The aftershocks and postseismic displacements appear to follow a similar relationship, although with different decay times. The temporal dependence of the two differs only by a term linear in time. Thus the temporal evolution of the afterslip seems to be consistent with a mechanism governed by frictional afterslip. Available rates of interseismic and postseismic deformation and coseismic static offsets allow us to approximately estimate a return period of about 400 years for great earthquakes in the Andaman region.

No abstract

No abstract

No abstract

.[1] We study temporal changes in seismicity in Sumatra-Andaman Islands region before the M 9.1 earthquake of December 26, 2004. We applied the epidemic type aftershock sequence (ETAS) models to the seismicity. The two-stage non-stationary ETAS model with a single change-point provides a better statistical fit to the seismicity data than the stationary ETAS model throughout the whole period. We made further change-point analysis of data sets by dividing into two sub-regions. The best fitted models suggest that the seismic activation relative to the ETAS rates started in the middle of July 2000 (about 4.5 years before the M 9.1 earthquake). This includes an increase in the background seismicity rates, particularly in the southern part of the seismogenic zone near the epicenter. A space-time ETAS model also suggests that the background seismicity throughout the entire Sumatra-Andaman Islands area had increased after the change-point time.Citation: Bansal, A. R., and Y. Ogata (2013), A non-stationary epidemic type aftershock sequence model for seismicity prior to the

No abstract

The depth determination from the gravity data in frequency domain is carried out using the classical fast Fourier transform (FFT) method utilizing scaling properties of ensemble of anomalous source. The problem of calculating power spectrum from the FFT is well described in the literature. Here, the application of other high-resolution methods of power spectrum calculation, such as maximum entropy method (MEM) and multi-taper method (MTM) are explored to estimate depth to anomalous sources. At the outset, the FFT, the MEM and the MTM are tested on synthetic gravity data, generated for different types of synthetic models and then all these methods are applied to the field gravity data of the Bengal basin. The MTM with scaling is found to be superior for providing the detailed subsurface information rather than the MEM and the FFT methods in the case of synthetic as well as field examples.