The Abandonment clause, an optional sub-clause of Events of Default, can be included to stipulate what happens to a lease if a tenant abandons the leased property.
1.1. Abandonment. Abandonment and vacation of the premises. Failure to occupy the premises for [fourteen (14)] consecutive days shall be deemed an abandonment.
From Matthew J. Marino, Partner, Allen Matkins LLP: "An unlawful detainer action is not required to regain possession of abandoned premises. Possession of abandoned premises can be obtained through an expedited procedure (approximately 18 days) that does not require a court order; however, rent must be due and unpaid for 14 consecutive days and the landlord must have "reasonable belief" that the tenant has abandoned and must have complied with certain statutory notice requirements."
Matthew J. Marino, Lease Workouts in Troubled Times- Handling Tenant Defaults, March 2009.