A closer view....

Looks very much like nutgrass, aka nutsedge.

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7432.html

Here is a link that might be useful: nutgrass

How often do you water your lawn? For those that doubt what I often tell anyone plagued by Yellow or Purple Nutsedge this, from Jean001as link, "Nutsedges are common weeds in landscapes and gardens in the coastal valleys, Central Valley, and southern areas of California. They thrive in waterlogged soil, and their presence often indicates drainage is poor, irrigation is too frequent, or sprinklers are leaky. Once established, however, they will tolerate normal irrigation conditions or drought." may provide some insight.
Where I see these sedges growing mostly is in lawns that are watered daily. I seldom see any growing in lawns that are properly, ie. infrequently and deeply, watered.