Israeli Physicists Uncover Material Fracture Mechanism Linked to Earthquakes

Scientists at the Hebrew University of Jerusalem have identified a previously poorly understood mechanism that precedes the sudden and catastrophic fracture of materials. This process, which begins with microscopic two-dimensional "spots" that expand very slowly, is now understood to be a critical precursor to material failure. The research, published in Physical Review Letters, reveals that these slow-growing crack "spots" expand at speeds ranging from microns to millimeters per second and occupy at least 75% of the total fracture process.

A linear, fast crack only forms when these slow-growing spots reach the thickness of the material itself. This new theory complements classical fracture mechanics by linking three distinct stages: initiation, creep, and explosive failure. Experiments also indicated that crack initiation occurs at scales ten times smaller than the Griffith length, the minimum crack size for unstable, rapid growth.

Researchers highlighted the universality of this mechanism, noting its applicability to both laboratory samples and natural phenomena like earthquakes. Professor Jay Fineberg, a co-author, stated that "Tensile fracture and frictional fracture may reflect the same basic geometric mechanism." Frictional fracture refers to the sudden slip between two surfaces when shear force exceeds static friction.

Understanding this hidden phase of crack initiation and development could lead to improved methods for detecting material defects before catastrophic failure. It also offers insights into the physics of earthquakes along geological faults, including the Dead Sea Rift, where major earthquakes occur roughly every 100-150 years, with the last significant event in 1927.