Abstract Database

TRAVEL TIME RESIDUALS FROM THE NEW AND OLD SEISMIC NETWORKS OF PAKISTAN AND PRELIMINARY HYPOCENTER DETERMINATION

MEE07163
Nasir Mahmood
Supervisor: Tatsuhiko HARA
Country: Pakistan
Abstractfulltext

The Pakistan Meteorological Department has started establishing a new digital seismic network in 2006. We evaluated data from this new network, and performed preliminary hypocenter determination. First, we checked detectability of new stations to find that the detection capability of the Islamabad station seems better than the Peshawar and Quetta stations in new network. Then, we calculated theoretical P and S wave travel times using USGS hypocenters. We compared them to the observed travel times from the new and old Pakistan seismic networks to obtain travel time residuals. For station Quetta in the old analog network, the P and S readings are less accurate than those from the new network. Taking these uncertainties into account, we performed preliminary hypocenter determination of events in the Hindu Kush region using data with relatively smaller residuals. We used two earth models: the one is iasp91 and the other has a crust structure from CRUST 2.0. Most of the events are located in the depth range consistent with USGS focal depths when we used iasp91, while the distances between the epicenters issued by the USGS and those determined using iasp91 are larger (on the order of 50 km ) than those when we used the latter model (on the order of 25 km). Probably due to the small number of data and not good station configuration to events in the Hindu Kush region, the dependence of hypocenters on crust models is strong. We expect it will be possible to improve accuracy of hypocenters by expanding our seismic network with carefully checking data.

Citation: Bulletin of IISEE, 43, 37-42.