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On the Study of Amplification in the Cerro Prieto Volcano, Mexicali Valley, Mexico Using Cross- and Auto-Power Spectrum Technique

Description: 

Based on previous reports of amplification on the Cerro Prieto volcano, we used a cross- and auto-power spectrum technique to corroborate this amplification. Due to the nonexistence of a reference site (with no amplification), to be used in the area of the volcano to know its true amplification; we tested the use of the spectral ratios (SR) of the cross-power (XP) spectrum of horizontal (H) and vertical (V) components (XPHV) and the auto-power (AP) spectrum of the vertical component (APV). The purpose is to find the true amplification on the volcano. We used time series of ambient noise and earthquake data recorded at ground surface to compute the spectral ratio between SR-XPHV/APV using ambient noise and earthquake data. Next, we compute similar Horizontal/Vertical Spectral Ratio (HVSR) but now among the Power Spectral Density (PSD) spectrum of horizontal and vertical components, we termed this variation the modified Nakamura Method when using ambient vibration data.

Preliminary results show that at the fundamental vibration frequency, the peak spectral amplitude when using SR-XPHV/APV are smaller when compared with the HVSR´s using PSD spectra. The fundamental frequencies obtained with both methods agree quite well. As an example, for one of the experimental sites (VCP) the obtained amplification factor is around 10 using earthquake data. However, when using ambient noise data the amplitude of the SR-XPHV/APV are at lower amplitude values; but the relative amplification when comparing with experimental sites between higher and low elevations, the amplification factor is around 11. In this way, the amplification on the Cerro Prieto volcano is corroborated using an alternative SR-XPHV/APV method. It is also noticed that when using ambient noise, the SR-XPHV/APV the spectral amplitudes at lower frequencies (~0.1Hz) are significant smaller in comparison with the ones obtained with the traditional HVSR using the PSD spectrum. The phase and coherence of the XPHV spectrum is also analyzed in terms of the energy correlation between the horizontal and the vertical signals.

Session: From Sensors and Networks to Site Characterization and Site Response: Coming Full Circle [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Carlos I. Huerta-López

Student Presenter: No

Invited Presentation: Yes

Authors