A note on parameters T0 and Vs30 for microzonation in southern Ensenada City, Baja California, Mexico

Una nota sobre los parámetros T0 y Vs30 para la microzonificación en la zona sur de la ciudad de Ensenada, Baja California, México

J. Antonio Vidal-Villegas1, *, Germán Martínez-Romo1, Patricia Andrade-García1

1 Departamento de Sismología, División de Ciencias de la Tierra, Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California. Carretera Ensenada-Tijuana 3918, Zona Playitas, Ensenada, 22860, Baja California, México.

* Corresponding author: (J. A. Vidal-Villegas) This email address is being protected from spambots. You need JavaScript enabled to view it.

How to cite this article:

Vidal-Villegas, J. A., Martínez-Romo, G., & Andrade-García, P. (2026). A note on parameters T0 and Vs30 for microzonation in southern Ensenada city, Baja California, Mexico. Boletín de la Sociedad Geológica Mexicana, 78(2), N261125. https://doi.org/10.18268/ BSGM2026v78n2N261125

Manuscript received: July 27, 2025. Corrected manuscript received: November 16, 2025. Manuscript accepted: November 19, 2025.

ABSTRACT

Seismic noise was collected to determine the natural period (T0) and shear-wave velocity (Vs30) south of Ensenada City (called “Ex Ejido Chapultepec”). This zone has had significant housing development. Short- and intermediate-period seismometers (2s and 10s, respectively) together with 24-bit recorders were used to record ambient noise. The parameter T0 was obtained using the HVSR technique, and Vs30 was obtained using the SPAC technique. Regarding the results, the T0 values range from 0.2 s to 2.4 s, and the velocity profiles exhibit Vs30 values ranging from 148 to 549 m/s. These values align with those of the local geology of the study area and are crucial for habitation design and seismic hazard studies in Ensenada City.

Keywords: microzonation, HVSR and SPAC methods, T0 and Vs30 parameters.