47 research outputs found
Multiple Diffractions of Elastic Shear Wawes by a Rigid Rectangular Foundation Embedded in an Elastic Half Space 1
A rigid rectangular foundation, embedded in an elasti
Basin Effects in Strong Ground Motion: A Case Study from the 2015 Gorkha, Nepal Earthquake
The term "basin effects" refers to entrapment and reverberation of earthquake
waves in soft sedimentary deposits underlain by concave basement rock
structures. Basin effects can significantly affect the amplitude, frequency and
duration of strong ground motion, while the cone-like geometry of the basin
edges gives rise to large amplitude surface waves through seismic wave
diffraction and energy focusing, a well-known characteristic of basin effects.
In this research, we study the role of basin effects in the mainshock ground
motion data recorded at the Kathmandu basin, Nepal during the 2015 Mw7.8 Gorkha
earthquake sequence. We specifically try to understand the source of the
unusual low frequency reverberating pulse that appeared systematically across
the basin, and the unexpected depletion of the ground surface motions from high
frequency components, especially away from the basin edges. In order to do that
we study the response of a 2D cross section of Kathmandu basin subjected to
vertically propagating plane SV waves. Despite the scarcity of geotechnical
information and of strong ground motion recordings, we show that an idealized
plane-strain elastic model with a simplified layered velocity structure can
capture surprisingly well the low frequency components of the basin ground
response. We finally couple the 2D elastic simulation with a 1D nonlinear
analysis of the shallow basin sediments. The 1D nonlinear approximation shows
improved performance over a larger frequency range relative to the first order
approximation of a 2D elastic layered basin response.Comment: Geotechnical Earthquake Engineering and Soil Dynamics V, Austin,
Texas (2018