Only if the mobile (or modular or manufactured) home is located in a city that requires it, ie city of Los Angeles, Malibu, Culver City, San Fernando etc. Here is a list of cities that require an installed seismic earthquake shut off valve when selling.
Check with the community or tract manager to see if there is an earthquake shut off valve to the main tract meter, which is then distributed to all homes with the tract, OR if each home has its own meter and gas bill from So Cal Gas.
If the gas bill is paid to So Cal Gas, an earthquake shut off valve is required.
If the gas bill is paid to the owner of the park/community, mostly like they are responsible for an earthquake shut off valve, and not the home owner.
Properties located in the un-incorporated areas of Los Angele County are not required to have an earthquake shut off valve when selling, ie Topanga Canyon, Aqua Dulce, and other areas.
Here is a photo of an installed seismic earthquake shut off valve on a gas meter for a mobile home. The automatic seismic valve goes between the gas meter and the flexible gas line that leads into the undercarriage of the mobile home.
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