Subsurface geological characteristics of Al-Ammariah area, Saudi arabia, for sustainable urban development using multichannel analysis of surface waves

Geological site characterization plays a vital role in the development and sustainability of urban projects. The Multichannel Analysis of Surface Waves (MASW) technique evaluates subsurface geological characteristics to support sustainable urban development in Al-Ammariah, Saudi Arabia. MASW data from 26 profiles in the area were analyzed to generate 1D and 2D shear wave velocity (Vs) geoseismic sections up to 30 m in depth, as well as two borehole geotechnical sections. The results enabled the classification of subsurface lithology into four distinct layers: the topmost layer with Vs values between 180 and 360 m/s; the 2nd layer has Vs ranging from 360 to 760 m/s; the 3rd layer of 15-20 m depth and Vs between 760 and 1500 m/s while the 4th layer extends below 20 m with Vs exceeding 1500 m/s. The bedrock depth has been estimated throughout the study area, varying significantly from 6 to 15 m, with shallower depths to the east and deeper depths to the west. The site of interest can be characterized according to National Earthquake Hazards Reduction Program (NEHRP) standards and entered into site class C based on Vs values for the soil section. However, it is classified into C and B site classes based on Vs30 values. Moreover, the soil section is classified as stiff soil (Class C) and covers the northern zone, while Site Class B covers the southern zone of the study area. Both boreholes reveal weak, compressible soils at shallow depths, characterized by low SPT N-values (N < 10), indicating a poor load-bearing capacity. In contrast, deeper layers exhibit higher N-values (N = 10-50), providing high stability. Very dense soils (N > 50) offer excellent load-bearing properties, although they may pose drilling challenges. RQD classifications reveal a shift from poor-quality rock (RQD < 50%) in shallow depths, indicating weathered or fractured rock, to good-to-excellent rock (RQD > 75%) at deeper levels, which is suitable for construction. The results offer valuable insights into subsurface variability, supporting informed decisions for foundation design, geotechnical solutions, and sustainable construction practices.