verification of receipt of warning notifications by local emergency managers. Within minutes of the initial notification of the CSWC by the WC/ATWC, Office of Emergency Services (OES) staff were paged and instructed to verify that the notification was received by the local government emergency managers. This verification process was not able to be completed in the northern most counties (those directly impacted by the earthquake and with the greatest potential for being affected by a tsunami) where telephone service was limited by excessive local use after the earthquake and where hundreds of residents had called 911 dispatch centers to report the earthquake. In Crescent City, Del Norte County, a single 911 dispatcher was overwhelmed by the call volume and was not able to receive calls from state personnel verifying receipt of the tsunami warning.
Given the short time span in Humboldt and Del Norte counties between earthquake shaking, issuance of the tsunami warning by the WC/ATWC, and possible tsunami wave arrival, this demand made it difficult for the CSWC and OES to expedite the warning process, a problem that was exacerbated by overloaded wire and cell telephone systems, inadequate staffing at the state and local government emergency operations centers, and limited training at the local government level.
Despite the confusion that was prompted by the conflicting message sent by the Pacific Tsunami Warning and Mitigation System (PTWS), the CSWC transmitted only the first TWC (from the WC/ATWC) warning using CALWAS. The NWS, following NOAA procedure, activated the Emergency Alert System (EAS) and broadcast the tsunami warning to the potentially impacted counties.
Six minutes following the transmission of the tsunami warning, the CSWC held a conference call between the OES Costal Regional Administrator and earthquake/tsunami specialists to remediate the confusion with personnel from counties that might be impacted. As noted above, overload of the local telephone system precluded OES staff from making contact with local officials in Humboldt and Del Norte counties. The state’s satellite telephone system (OASIS) linking OES regional offices and county PSAPs could not be immediately utilized because it could not be accessed from staff residences (the event occurred when OES region staff were at home, as were most local government officials).
Another element of the states’ communication procedures with local governments is the convening of conference calls between local government emergency managers, state officials, and appropriate hazard experts at the time of the issuance of alerts to local government. The state maintains multiple 30-port conference bridge lines for this purpose. Attempts to use the conference call procedures at the time of the tsunami warning were unsuccessful because inbound lines with the scientists at the WC/ATWC were overloaded and local government officials could not be contacted.
As noted above, the population of the impacted areas in northern California was “notified” by the earthquake, by broadcasts over the NOAA All Hazards Radio system, and by stations participating in the EAS. In Crescent City, the tsunami sirens were not sounded until 8:30 PDT (0330 UTC) because of the telephone saturation of the 911 dispatch center and the inability of the single staff person on duty to handle conflicting workload priorities. Spontaneous evacuations took place in several communities. In many of the northern California communities,