"Crush injury and crush syndrome may result from structural collapse during an earthquake. Crush injury is defined as compression of extremities or other parts of the body that causes muscle swelling and/or neurological disturbances in the affected areas of the body. Typically affected areas of the body include lower extremities, upper extremities, and trunk. Crush syndrome is localized crush injury with systemic manifestations. These systemic effects are caused by a traumatic rhabdomyolysis (muscle breakdown) and the release of potentially toxic muscle cell components and electrolytes into the circulatory system. Crush syndrome can cause local tissue injury, organ dysfunction, and metabolic abnormalities, including acidosis, hyperkalemia, and hypocalcemia. Previous experience with earthquakes that caused major structural damage has demonstrated that the incidence of crush syndrome is 2-15% with approximately 50% of those with crush syndrome developing acute renal failure and over 50% needing fasciotomy. Of those with renal failure, 50% need dialysis."
Centers for Disease Control and Prevention: http://www.cdc.gov