The Effect of Secondary Arrivals on Regional Earthquake Locations


Synthetic Tests, Part 1

Synthetic data runs/relocations were performed for the select EDR events shown in the previous page, bottom figure, using the same arrival sets but varying how the arrivals were weighted. Only regional stations shown in Figure 1 were used. Two different velocity models were used for comparison: IASPEI and the SSB [Jih, 1998] (Introduction, Right Figure). Synthetic arrival times were first generated without added noise to test if station distribution was sufficient to accurately locate the events, given a known velocity model (Below). We then performed 10 sets of arrival time generation/location, adding gaussian noise to the P and S arrival data to simulate picking errors (Next Page). Starting locations were set to the actual synthetic event locations.

Relocations and error ellipses of synthetic arrival data with no gaussian noise added. Only the IASP91 relocations are shown, with and without defining S phases ("regional" arrival errors, see next page, Column D). Black dots are original synthetic locations. All arrival weighting schemes produced basically the same results. All events are relocated to the synthetic origins. Note that the error ellipses do decrease in size when S phases are defining.

   
S Defined S Not Defined


Introduction | Catalog Locations with Secondary Phases | Ground Truth Constraints on Relocations Near a Large-Magnitude Event
Synthetic Tests Pt. 1 | Synthetic Tests Pt. 2 | Relocations of Actual Data | Relocations Using S Phases for the Asia Study Area | Summary