Raw accelerometric data at station DMG is presented in downloadable form for the events associated with the 25 April earthquake in Gorkha, Nepal. In the main paper, only the records of the DMG station are analyzed. This supplementary material presents a similar preliminary analysis of the signals recorded at the NQ.KATNP station. NQ.KATNP and DMG are separated by a distance of about 800 m. Figure S1 presents the acceleration time histories, Figure S2 the Fourier acceleration spectra (FAS) and the horizontal-to-vertical ratios (HVSRs), and Figure S3 the time–frequency analysis and the results of polarization.
The raw accelerometric data recorded at station DMG and presented in Table 1 of the main article are provided. The records are in g and available for the three components: north, west, and down. The station is instrumented with a Geosig-AC23 sensor and a GSR24 digitizer (Bhattarai et al., 2011) installed on a concrete slab in a single story building. The parameters are shown below.
Download: Accelerometric_Data.zip [Zip Archive of ASCII Text Files; ~12.1 MB]. This zip archive contains the following raw data for the 25 April mainshock and the 26 April and 12 May aftershocks: time (s), and acceleration (g) for the north, west, and down directions.
The acceleration time histories at NQ.KATNP (Fig. S1) are quite similar to the records of DMG station, providing confirmation of the fidelity of both recordings. For DMG records, a predominant peak of 0.2 Hz is observed for the mainshock and the aftershock from HVSR (Fig. S2). Based on polarization analysis results (Fig. S3), for this frequency of 0.2 Hz, the motion is mainly concentrated on the horizontal component for both the mainshock and the aftershock (dip value around 0° on Fig. S3d and i) in a manner similar to that observed at the DMG station.
Figure S1. Acceleration time histories in g at station NQ.KATPN from the U.S. Geological Survey for (a) the 25 April Mw 7.8 mainshock and (b) the 12 May Mw 7.3 aftershock (20 s of pre-event noise are removed from the raw accelerograms). N, E, and U correspond respectively to north, east, and up components. The normalized Husid diagrams are represented on the second axis (grey solid lines). The time corresponding to 5% and 95% of the cumulative Arias intensity are also represented (dashed grey lines). The peak ground acceleration (PGA) and the significant relative duration Dsr(5%–95%) are also indicated for each component.
Figure S2. (Left) Fourier acceleration spectra (FAS) and (right) horizontal-to-vertical spectral ratios (HVSR) for (a) the 25 April Mw 7.8 mainshock and (b) the 12 May Mw 7.3 aftershock recorded at NQ.KATNP. FAS are smoothed according to the Konno and Ohmachi (1998) smoothing with b=30. FAS and HVSRs are represented on the frequency band for which the signal is larger than the noise.
Figure S3. Analysis of the mainshock event (left) and the aftershock (right) recorded at NQ.KATNP. (a) and (f) Amplitude of the S-transform (ST) of the horizontal components normalized by the maximum of the total amplitude, defined as in which t is the time and f is the frequency. (b) and (g) amplitude of the ST of the vertical component normalized by STmax (please note that the amplitude values above 1 may be clipped by the color scale in some places, leading to some yellow patches); (c) and (h) ellipticity attribute; (d) and (i) dip attribute; (e) and (j) azimuth attribute. In plots (c–e) and (h–j), opacity has been used to highlight the values at which the total amplitude is larger than an arbitrary threshold, lighter colors are for values between 0.1 and 0.5, and brighter colors are for values above 0.5.
Bhattarai, M., U. Gautam, R. Pandey, L. Bollinger, B. Hernandez, and V. Boutin, (2011). Capturing first records at the NSC accelerometric network, Nepal, J. Nepal Geol. Soc. 43, 15–22.
Konno K., and T. Ohmachi (1998). Ground-motion characteristics estimated from spectral ratio between horizontal and vertical components of microtremor. Bull. Seismol. Soc. Am. 88, no. 1, 228–241.
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