**5.1 The failure of traditional construction patterns**

This earthquake hit the province of Al Hoceima, especially the city so named, the municipality of Imzourem and the villages of Ait Kamra and Izemmouren. The rural houses in this geographical area of Morocco, most of them of vulnerability class A, were built using the traditional construction pattern, very similar to those we have just highlighted in the most rustic areas of the Algarve, with more emphasis in Fonte de Louzeiros: single-story load-bearing walls made with unworked raw materials and unskilled masonry techniques, supporting a brittle roof of wooden logs in parallel under a bed of reeds tied together with rope or wire, all covered by a layer of water-repellent mortar and, occasionally, with a plastic film interposed acting as waterproof element (**Figure 13a**). The load-bearing walls were made up

#### **Figure 13.**

*Ait Kamra, traditional house pattern: (a) partial collapse showing the doble-leaf load-bearing walls, fieldstone masonry bonded with mud mortar and roof of wooden logs and canes covered with a plastic film (blue) and layer of water-repellent mortar (grade 4, class A); (b) handmade joist of hollow bricks assembled with a single steel rod. Source: P Murphy.*

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**Figure 14.**

*Ait Kamara, corner failure pulling down the roof slab (grade 4, class A). Source: P Murphy.*

*Effects of Earthquakes on Buildings in the Ibero-Maghrebian Region*

of two faces of field stone masonry (double-leaf) not anchored between them, and poorly bonded with high porosity and low adhesion mud mortar. The bending of the walls in both directions due to reverse horizontal forces caused the inner detachment of the double-leaf masonry and the subsequent bowing, peeling, and overturning or collapse of the external skin. Shear cracks also caused widespread wall collapses and massive corner failures and fall of roofs, pulling down huge amounts of debris (**Figure 14**). The use of hollow bricks assembled with a single steel rod to form a handmade joist as reinforcing element for the roof did not provide greater rigidity or better connection between roofs and load-bearing walls (**Figure 13b**).

Regardless of the function of the walls (infill, load-bearing, retaining, etc.), type of building materials (adobe, stone, brick, gray concrete block…) and vulnerability class (A, B, C…), not all cracks should be exclusively interpreted as a result of seismic shaking. In general, wall cracks are caused by the effect of five recognized forces: tension, compression, bending, torsion, or shearing. But only when cracks have a diagonal shape it can be inferred that they have been generated by shear stress or a combined effect tension-shearing or bending-shearing. Shear or diagonal cracks may be due to earthquakes, but also―and most frequently―to a slope in the ground, poor foundations, landslide, soil composition (i.e., expansive clays), geological conditions, etc., which can lead to subsidence or settlement processes. In April 2019, during a brief field visit to the Roman ruins of Baelo Claudia (Tarifa, Spain), an ancient city where some geologists have believed to find evidence of great destruction caused by a sequence of earthquakes between the 1st and 3rd centuries BC, we certainly observed shear cracks in the *summa cavea* of the theatre, bowing of a load-bearing wall in a *vomitorium* arch, and expulsion of voussoirs in another arch near the *parascenium* that looked like piano keys shifted (**Figure 15**). We can firmly state that these structural damages were not induced by earthquakes because they occurred after the reconstruction works of this archeological site carried out in the 1980s and without seismic events to justify them. Rather, these

*DOI: http://dx.doi.org/10.5772/intechopen.94739*

**5.2 X-shaped damage, a seismic evidence**

*Effects of Earthquakes on Buildings in the Ibero-Maghrebian Region DOI: http://dx.doi.org/10.5772/intechopen.94739*

of two faces of field stone masonry (double-leaf) not anchored between them, and poorly bonded with high porosity and low adhesion mud mortar. The bending of the walls in both directions due to reverse horizontal forces caused the inner detachment of the double-leaf masonry and the subsequent bowing, peeling, and overturning or collapse of the external skin. Shear cracks also caused widespread wall collapses and massive corner failures and fall of roofs, pulling down huge amounts of debris (**Figure 14**). The use of hollow bricks assembled with a single steel rod to form a handmade joist as reinforcing element for the roof did not provide greater rigidity or better connection between roofs and load-bearing walls (**Figure 13b**).
