By T. Jayani, JadeTimes News
Fifty years after the first mobile phone call, the technology in our pockets is helping build the world's largest earthquake detection system.
On October 25, 2022, a 5.1 magnitude earthquake shook California’s Bay Area. It was mild, with no reported damage, but significant because many residents received alerts on their phones before feeling the tremors. Similarly, on August 6, 2024, Southern California residents were alerted up to 30 seconds before a 5.2 magnitude quake near Bakersfield. Remarkably, these phones also played a role in detecting the earthquakes.
Google, in collaboration with the United States Geological Survey (USGS) and various California universities, developed an early warning system that alerts users seconds before an earthquake's tremors reach them. These precious seconds can provide enough time to take cover, slow down trains, halt planes, and keep cars off bridges or tunnels, potentially saving lives during stronger quakes.
The system uses data from two sources. Initially, it relied on 700 seismometers across California, installed by USGS, the California Institute of Technology, UC Berkeley, and the state government. Seismometers in Oregon and Washington also contribute to this system, known as ShakeAlert. Additionally, Google has been leveraging smartphones running its Android operating system to create the world's largest earthquake detection network.
Most Android phones have accelerometers that detect phone movements. These sensors, typically used for screen orientation and step counting, can also function like mini seismometers. Google introduced a feature that allows phones to automatically send data to the Android Earthquake Alerts System if they detect vibrations characteristic of earthquake P waves. By combining data from numerous phones, the system can determine if an earthquake is occurring and send alerts to nearby areas before the seismic waves hit.
Since radio signals travel faster than seismic waves, alerts can reach users before the shaking starts. Marc Stogaitis, an Android software engineer, explains, "We’re essentially racing the speed of light (signals from a phone) against the speed of an earthquake, and the speed of light is much faster."
This technology enables earthquake monitoring in regions lacking expensive seismometer networks, offering potential alerts in remote and underprivileged areas. California, experiencing up to 100 small quakes daily, is a prime testbed for this system. In October 2022, phones across the San Francisco Bay Area detected seismic waves from an earthquake, showcasing the system's capabilities.
The USGS's ShakeAlert now regularly triggers alerts on mobile phones when seismic activity crosses key thresholds. The MyShake App, developed by UC Berkeley researchers, also turns stationary phones into detectors and sends location based alerts. California typically experiences 15-20 earthquakes above magnitude 4.0 annually.
Globally, of the estimated 16 billion mobile phones in use, over three billion run Android, with the Earthquake Alerts System available in over 90 earthquake prone countries. However, the system has limitations in remote areas with few phones and offshore quakes that can cause tsunamis. While it provides brief advance alerts, predicting earthquakes before they occur remains a challenge.
