Earthquake location by arrival times
= Earthquake location by arrival times
{title2=$t_i=t_0+T_i(\mathbf x)$}
Arrival-time location estimates a <hypocenter> and origin time by comparing picked phase arrivals with predicted <travel times>. <Linearization> gives residual changes $\delta t_i=\delta t_0+\nabla T_i\cdot\delta\mathbf x$. Poorly distinct <derivative> columns cause tradeoffs, while incorrect <wave speeds> or phase labels cause systematic bias even with many stations.