Los Angeles Basin is a sedimentary basin that is located in Southern California, also called the peninsular region. It is marked with elongated low hills and ridges that group, the hills located on the east of pacific. There are rapid transgression and regression of shoreline moving the area to a shallow marine environment.
This region is divided into four major basins central, southwest, northwest, and northeast structural blocks. The history of the basin begins with the subduction of the Pacific plate under the North American plate in the Mesozoic era.
After The subduction, the Pacific Monterey plate creased and the plate margin was transformed into a transform boundary. Earlier in Miocene high heat flow and transmission caused extension of the basin.
It's Due to the basin lies in the boundary of the traversing and peninsular ranges, the basin experiences both compression, and strike-slip tectonics. During the early Pliocene which later also identified as the phases of deformation of folding as a result of fault movements and slight rotation events.
I know that Boston is a main port of the American Economics, so they would want it for exporting and importing goods. I would assume that Philadelphia would have a related cause.
