Background
Earthquake and Tsunami Warning System (ETWS) is used to deliver timely emergency information about earthquakes and tsunamis to the public, guiding evacuation and self-rescue.
However, currently this function is disabled by default on most commercial phones, so when an earthquake approaches phones may not display alert popups and countdowns, leaving people without necessary time to escape.
Field findings: many users did not enable the feature
During the recent Gansu earthquake in China, ZTE deployed more than 60 engineers to coordinate with carriers for on-site support, remote assistance, and emergency handling. ZTE telecommunications support specialists carried key spare parts for wireless, core, and transport networks and some relief supplies to the disaster area.
Analysis of collected data showed that many users had not enabled the earthquake warning feature when the earthquake occurred.
Wireless base station PWS principle
The public warning system (PWS) includes ETWS and the Commercial Mobile Alert System (CMAS) and other alert messages.
CMAS and ETWS alert messages are notified by the core network (AMF) to base stations (gNodeB/eNodeB) and broadcast to UEs via cell system information. CMAS messages are delivered via SIB8; ETWS uses SIB6 and SIB7. The ETWS primary alert notification (time-critical warnings such as imminent earthquake or tsunami) is sent in SIB6; ETWS secondary alert notifications (less time-critical information such as post-quake evacuation routes or food distribution) are sent in SIB7.
PWS alert messages are generated by the cell broadcast entity (CBE), passed through the cell broadcast center (CBC) and AMF to the base station. The base station converts the alert into system information blocks (SIB6/SIB7/SIB8) and transmits them on the Uu interface. See 3GPP TS 23.401-a60 for details. The diagram below shows the standard flow for wireless broadcast messages (from section 9.1.3.4.2 of TS 23.401-a60).
Note: Broadcasting earthquake warnings via base station SIB messages is one of several delivery methods. Alerts can also be broadcast over Wi-Fi, television, loudspeakers, and other channels.
Enabling the feature
Methods to enable earthquake alerts vary slightly across phone brands. Most phones allow enabling the feature by searching for "earthquake alert" in Settings.
Popup alerts
When earthquake alerts are enabled, phones typically display a popup alert when an earthquake is imminent. This provides time to move to a "triangle of life" area (a small triangular space formed next to large furniture where occupants can shelter from falling ceiling debris), designated shelters, or other safe locations to reduce risk and protect life.
Advise family and friends to enable earthquake alerts so they can prepare if a hazard approaches.
