| Attribute | Format | Summary Description | Index |
| HYPID | NUMBER(8) | First half of pimary key on this table | n |
| PHID | NUMBER(8) | Second half of primary key on this table | n |
| DEPRECATED | VARCHAR2(1) | Status of the association entry | |
| PHASE | VARCHAR2(8) | Phase name | |
| PHASE_FIXED | VARCHAR2(1) | Flag, set if automatic update forbidden | |
| NET | VARCHAR2(6) | Network code of associated station | |
| STA | VARCHAR2(6) | Station code of associated station | |
| DELTA | NUMBER(6,3) | Distance between station and hypocenter | |
| SEAZ | NUMBER(6,3) | Station to event azimuth | |
| ESAZ | NUMBER(6,3) | Event to station azimuth | |
| TIMEDEF | VARCHAR2(1) | Flag, set if time constrains hypocenter | |
| AZIMDEF | VARCHAR2(1) | Flag, set if azimuth constrains hypocenter | |
| SLOWDEF | VARCHAR2(1) | Flag, set if slowness constrains hypocenter | |
| TIMERES | NUMBER(6,3) | Travel time residual (seconds) | |
| AZIMRES | NUMBER(6,3) | Azimuth residual (degrees) | |
| SLOWRES | NUMBER(6,3) | Slowness residual (degrees) | |
| WEIGHT | NUMBER(4,3) | Posterior weight of the arrival time | |
| AUTHOR | VARCHAR2(16) | Code of agency that created association | |
| REPORTER | VARCHAR2(16) | Agency that reported association to ISC | |
| LDDATE | DATE | Date loaded in ISC database | |
| MODDATE | DATE | Last date modified | |
| REMID | NUMBER(8) | External key to remark table |
The association relation stores association of phases with hypocenters. A separate association row for each phase is required to store information that differs for each phase in a reading, such as the residuals. A phase may be associated with several hypocenters (e.g., a hypocenter reported by another agency as well as preliminary and final ISC hypocenters).
For reported associations, a row in the association relation is the most faithful possible representation of the report. Thus, distance, azimuths, residuals and weights are non-null in the association relation only if explicitly reported. If a report includes inconsistent data (e.g., incorrect delta for a station and epicentre) then they will be entered inconsistently in the row for the reported association. The exception to this faithful representation of the report is association.phase, which may be an interpretation of the reported identification. For example, if a phase is identified as 'EP' in a report, phase.phase will be 'EP' while association.phase may be 'P'.
If the ISC associates the phase with its own epicentre then an additional row will be inserted in the association relation, perhaps with a new phase identification. The association.phase attribute is the phase identification used in computing the hypocenter and the residuals in the association relation.