Whisk together the water, orange juice, 1/2 cup salt, light brown sugar, garlic powder, oregano, and thyme in a large glass or ceramic bowl. Submerge the pork chops in the brine. Cover the bowl with plastic wrap, and brine in the refrigerator for 1 hour.
Heat grapefruit juice, 1/4 cup brown sugar, and red pepper flakes in a saucepan. Cook and stir until sugar is dissolved and mixture comes to a boil; reduce heat and cook until syrupy, about 15 minutes.
Brown the pork chops in a pan with some of the brine and baste the pork chops with the syrup as they cook.
An instant-read thermometer inserted into the center should read 145 degrees F (63 degrees C).
Place the remaining fresh grapefruit sections on the pork and drizzle relish over the top.