The elastic deformation is reversed but the slippage is not. An advantage of gears is that the teeth of a gear prevent slippage. Some of the seaward slippage of the flank occurs aseismically, without noticeable earthquakes. Leno weave produces an open fabric with almost no yarn slippage or misplacement of threads. This further stabilized and supported the valve, decreasing valve slippage. Earthquakes are caused by slippage within geological faults. Lawn tennis rackets originally flared outward at the bottom of the handle to prevent slippage. Evolutionary changes from replication slippage also occur in simpler organisms. The TORSEN unit varies power distribution as needed, based on steering angle and wheel slippage. For certain applications, the slippage inherent in automatic transmissions can be advantageous. This left the two sets of four duplex driving wheels susceptible to wheel slippage. The result is no slippage, and virtually no power loss. It was quickly determined that focus on customer experience was key in reversing the slippage. In other cases, "slippage", a shift in the exact time target, occurs. Bateson believed that these self-correcting systems were conservative by controlling exponential slippage.