Combine the olive oil, soy sauce, sesame oil, ginger, maple syrup, Chinese mustard, sriracha and garlic in a large bowl. Pour one-third into a small bowl and reserve. Add the salmon fillets to the large bowl. Marinate, covered, in the refrigerator for 30 minutes.
Heat a large nonstick skillet over medium-high heat. Add a drizzle of olive oil to coat the skillet. Add the salmon skin-side down and cook until crispy, about 5 minutes. Baste the flesh side with the reserved marinade. Flip and cook until the salmon is cooked through and the flesh side is golden brown, an additional 3 to 4 minutes. Top with the scallions.