3D VISUALIZATION OF GEOLOGIC, GEODETIC, AND SEISMIC DATA FROM THE APRIL - MAY 2015, NEPAL, EARTHQUAKE DOUBLET

The availability of tools for simultaneous 3-D visualization of different types of data is valuable for quick analysis of the setting of a major earthquake. 3-D visualization allows for rapid identification of inconsistencies in the preliminary data that are realeased after an earthquake, and it can aid in deciding what other data may be needed.

The M_w 7.8 and M_w 7.3 Nepal earthquakes of April - May 2015 form a doublet, as the magnitude difference between them is only 0.5, they are close in both space and time, and each event shows a typical aftershocks sequence. We used the 3-D modeling and visualization software Gocad^TM in the first few days after the M_w 7.8 event to better understand how the seismologic and geodetic data that became available shortly after the event fit with the known regional tectonic context. In the first couple of days after the M_w 7.8 earthquake, we first built a 3-D model of the fault based on published works, from which it became clear that the earthquake involved the lower thrust ramp rather than the flat. We were also able to build, within a week of the M_w 7.8 event, a reasonable 3-D model of the static Coulomb stress change in the volume surrounding the earthquake, which showed how significant stress built up both on the MFT flat, and on the ramp itself further east, where the M_w 7.3 earthquake occurred.