Depth Phase Depth Calculation
Once a solution has converged for
a given event an attempt is made to calculate a depth phase depth for that
event using the differences in arrival time between pairs of P and pP phases
at the same station (calc_depdp). It is also possible for the operator to give the fix_on_depdp
instruction and do this calculation at the start of each iteration, using
the resulting depth as a fixed depth for that iteration. In this case
the depth and depth phase depth for a solution will be the same unless the
depth phase depth is changed by the final calculation done for all events
- very unlikely as the solution and depth phase depth have already been through
several iterations together.
Each phase structure has 4 members related to depth phase depth calculation:
- pP_weight - number between 0 and 1. Set in function solve_depdp
depending on pP_resid.
- pP_resid - difference between observed P time minus pP time and corresponding value from tables. Set in function calc_pP_resid.
- pP_dtdh - derivative of time with respect to distance in seconds per degree. Set in function jb_pP_P.
- pP_P_time - theoretical difference between P arrival time and pP arrival time. Set in function jb_pP_P.
The solution structure has 2 members related to depth phase depth calculation:
- depdp - depth calculated from P minus pP times. Set in function solve_depdp.
- depdp_error - standard error in depth phase depth. Set in function solve_depdp.
The event structure has 1 member related to depth phase depth calculation:
- fix_on_depdp - either 0 or 1. Set in function read_instruction. Will be 0 unless fix_on_depdp is included on the instruction line for this event by the operator.