Sector 4: zone of in situ accretion: Europeans who married natives.
Disamenity are sectors which are poor land area: city dump, hillside, rocky, flood plain, etc. When rural poor would move to big LDC cities for jobs, they would arrive with no money and sleep on the streets or in abandoned buildings of the disamenity. Then they would begin looking for scavenged items to build a shack in the "periferico" sectors.
Periferico are sectors that house squatter settlements. Families erect primitive shelters with scavenged cardboard, wood boxes, sack cloth, and crushed beverage cans. As they find new bits of material, they add them to their shacks. Perhaps later they can build a tin roof or partition space into rooms, and the structure acquires a more permanent appearance.