This is the definition of relocation diffusion. Stimulus, contagious, and hierarchical diffusion are all kinds of expansion diffusion. Expansion diffusion is when innovations spread to new places while staying strong in their original locations. For example, Islam has spread throughout the world, yet stayed strong in the Middle East, where it was founded.

A “modern cultural hearth” is defined as a global center of culture and economics with a worldwide influence (i.e. Tokyo, Paris, London, New York City, and Los Angeles). Despite its large population, Mexico City’s culture and economic exports do not match those of cities described as modern cultural hearths. Generally, a modern cultural hearth is a highly populated city in an extremely wealthy and culturally influential country (i.e. the United States, Japan, and China).

A “cultural hearth” is a place of origin for a widespread cultural trend. For example modern “cultural hearths” include New York City, Los Angeles, and London because these cities produce a large amount of cultural exports that are influential throughout much of the modern world. Ancient cultural hearths include, Mesopotamia, the Nile River Valley, and the Wei-Huang River Valley.

All cities, particular large metropolises like New York City and Paris, exert a pull on the area around them. This influence is social, economic, and political. People are drawn to large cities because of the abundance of opportunity that comes with having so many people in such a relatively small space. The farthest reach of a city’s social and economic influence is known as its “breaking point.” For example, London’s breaking point is probably the north coast of France, after which the influence of Paris far exceeds the influence of London.

Ancient cultural hearths are places where civilization first sprang up during the agricultural revolution that took place roughly eight to ten thousand years ago. All of these are notable places where the agricultural revolution took place except the Mississippi River Valley, which was not settled in large numbers until much later.

While diffusion is the more general movement of ideas, notions, and innovations, it can be broken down in its more specific functions. Contagious diffusion requires direct person-to-person contact, not the influence of trends observed in this question. Expansion diffusion deals with a single population, and so is insufficient for this multi-city movement. Diffusion by relocation is a sequential process in which the ideas are transmitted by their carrier agents (such as immigrants) as they evacuate old areas and relocate to new ones. While more appropriate than the first two, relocation is not quite as accurate an answer as hierarchical: a form of diffusion in which an idea spreads by trickling down from larger to smaller adoption units. Fashion is not being carried by people as they leave the larger cities, but is rather observed and adopted by smaller cities that don't have the means or resources to generate such ideas on their own.

Most people understand globalization to be a recent phenomenon - the permeation of American culture and consumerism around the world. However, globalization is a relatively old phenomenon as it only really describes the global homogenization of culture and experience through one dominant cultural tradition. What primarily separates the modern wave of globalization from previous iterations is the instantaneous telecommunication afforded by inventions like the internet. This connects people around the world instantly and has dramatically shortened the time taken to exchange media and ideas.

When an idea diffuses from its origin, but is changed or modified as it is adopted in other places, it is characterized as stimulus expansion diffusion, as opposed to being diffused in its original form (contagious expansion diffusion), diffusing from higher levels to lower levels (hierarchical expansion diffusion), or diffused by adherents moving into other regions (relocation diffusion).

Contagious diffusion involves a form of expansion in which people near the point of origin become adopters of a cultural fad. In the example above, the point of origin is the celebrity, and the townspeople become adopters of the Brand X fad. 

Diffusion is the spread of an idea or characteristic over time. When people move, or relocate, they spread ideas along with them. Therefore this is called relocation diffusion. "Distance decay" describes the process whereby interaction between locales decreases as distance increases.