Improve gmfs for Nepal/Gorkha event

[CatalinaYepes]

The current gmfs indicated for Gorkha can be improved by:

• Add rupture model and estimates from the rupture geometry defined by Stevens et al. 2018
• Include gmpe logic tree from NSET
• Evaluate and incorporate macroseismic information to condition gmf

The following studies consider macroseismic data for the characterisation of the ground shaking:

1. Martin SS, Hough SE and Hung C (2015) Ground motions from the 2015 Mw 7.8 Gorkha, Nepal, Earthquake constrained by a detailed assessment of macroseismic data. Seismological Research Letters 86(6): 1524–1532. DOI: 10.1785/0220150138. https://doi.org/10.1785/0220150138
2. Hough SE, Martin SS, Gahalaut V, et al. (2016) A comparison of observed and predicted ground motions from the 2015 MW7.8 Gorkha, Nepal, earthquake. Natural Hazards 84(3). Springer Netherlands: 1661–1684. DOI: 10.1007/s11069-016-2505-8. https://doi.org/10.1007/s11069-016-2505-8
3. Adhikari SR, Baysal G, Dixit A, et al. (2017) Toward a unified near-field intensity map of the 2015 Mw 7.8 Gorkha, Nepal, Earthquake. Earthquake Spectra 33(Special issue 1): S21–S34. DOI: 10.1193/120716EQS226M. https://doi.org/10.1193/120716eqs226m
4. McGowan SM, Jaiswal KS and Wald DJ (2017) Using structural damage statistics to derive macroseismic intensity within the Kathmandu valley for the 2015 M7.8 Gorkha, Nepal earthquake. Tectonophysics 714–715. Elsevier B.V.: 158–172. DOI: 10.1016/j.tecto.2016.08.002. https://doi.org/10.1016/j.tecto.2016.08.002
5. Adhikari, Sujan & Guragain, Ramesh & Murakami, Hitomi. (2016). Study on shaking intensity distribution of the 2015 Gorkha earthquake in Nepal. Conference: International workshop on the first memorial day of 25th April, 2015, Gorkha Earthquake at Kathmandu, Volume: I.

[CatalinaYepes]

The commit 3fc81b6 includes gmpe logic tree from NSET and the corresponding calculations

[CatalinaYepes]

Better to leave for further study the incorporation of macroseismic information to condition gmf