Morphobathymetry

A synthesis of available hathymetric data from the Romanche region, including our own and those of MONTI1991, HONNOREZ1991 and SEARLE1994 is presented in simplified form in Fig. 3. These bathymetric data have been processed to produce a shaded relief map of the Romanehe region (Fig. 4). The results of a close-spaced survey of a limited area near the eastern RTI is shown in Fig. 5.

Of the many features shown by these maps, we note that: (a) the eastern RTI is not well defined morphologically, contrary to the western RTI (where, however, data coverage in not as good); (b) a more or less continuous aseismic valley is observed to the north of the active transform valley; the aseismic valley merges into the active valley near the eastern RTI; (c) the transverse ridge rises prominently on the northern side of the transform, reaching its maximum relief in an area opposite the eastern RTI; (d) the active transform valley, defined on the base of earthquake epicenters, is not straight but has it few bends in its orientation.

Bathymetric data from MONTI1991 and SEARLE1994 and from this work were digitized, merged and edited at IGM-CNR of Bologna. After processing with a regular-gridding program, the maps of` Figs. 3, 4, 5, 6 and 7 were produced.

Figure 4: Shaded relief map of the Romanche Transform Region, derived by bathymetric data. Shaded relief map was obtained assuming illumination from NW 45°over the horizon. Horizontal resolution is 1KM, no vertical exageration. Mercator projection at 0°.