An earthquake can be an imperceptible ground shaking to a violent movement caused by the sudden displacement of rock materials below the surface of the earth.

Two types of earthquakes may occur (tectonic or volcanic), but only tectonic earthquakes caused by sudden displacement along faults in the earth’s construction may affect Mandaluyong which is near the West Valley Fault.

Fortunately, Mandaluyong sits on an adobe bedrock covered by a thin layer of soil and is classified as within a Very Low Risk area least likely to be affected by high intensity earthquakes.

Consequently, the risk of liquefaction, which is closely associated with earthquakes and loosely packed soils and saturated sediments, is very minimal in Mandaluyong. (Map 4 Foundation Engineering and Map 5 Landslide Prone Areas)

Typhoons during the wet season greatly affect the city and the rest of Metro Manila. Damage to property and risk of lives are among the major effects of typhoon. Secondary to these are the flash floods that severely affect the lowland areas.

Heavy rains, even of short duration, results to flooding in some areas of Mandaluyong. Most prone to flooding are barangays Planview along Maysilo Circle, New Zaniga along P. Cruz and Boni Ave., Hagdang Bato Ibaba along Shaw Boulevard and Acacia Lane. However, for 2-10 years flood cycle, these areas expand to cover barangays lining the coasts of Pasig and San Juan Rivers. These correspond to areas shown yellow in Map 6 (Flood Prone Areas).