# Recent Advances in Internet of Things Solutions for Early Warning Systems: A Review
## 5 Earthquakes
### Reviewed Use Cases for Earthquakes EW
Alerts can be generated by either detecting p-waves using the sensors embedded in the user's smartphones or mining data from regional seismic networks (for example, it currently receives data from the ShakeAlert system in the US). While the smartphones approach makes the deployment of the network very easy, characterizing the parameters of the earthquake (location, magnitude, and origin time) is dependent on the number and geographic distribution of phones with the MyShake app around the event. An ANN embedded in the smartphone app is used to distinguish between earthquake-like ground motions and everyday motions. When an earthquake event is triggered on the phones, the MyShake server looks for space-time clusters of triggers to confirm that an earthquake is underway. While the app can provide earthquake detection, location, magnitude estimation, and shake maps, current effort is on improving its early warning capabilities. A simulation platform was created to test the early warning capabilities of the system. The simulation showed that an issue can be alerted 15.6 s before a densely populated area is reached by the earthquake, but there are 2.8 s of delay to forward the alert from the MyShake server to the cellphones, and it is not clear how this delay would scale with a large number of devices in a real scenario. The predicted magnitude was lower than the observed one. The new version of the app MyShake2.0 will issue and receive earthquake early warning alerts and improve the overall characteristics of the app. [PERSON] et al. [67] began the development of a low-cost, low-power and cloud-based earthquake alert system called Earthcloud which uses geophones instead of MEMS accelerometers, claiming they offer less noise at lower sampling frequency. When variations in ground motion are detected, sensors send data to a server and also produce a first alarm if the motion is strong enough. Specifically, the data is encapsulated into an MQTT packet and forwarded to the Amazon Web Services (AWS) IoT Core which processes and then sends them to Amazon Kinesis. Amazon Kinesis is used for pre-processing but also to forward data in real-time to both connected devices (which would receive a second confirmation alarm or a first alarm if the sensors initially did not trigger any alarm by themselves) and Amazon S3, a data storage service. The developed solution was tested using a three-unit network in the city of Modena, Italy, and only one out of the three sensors failed to detect an earthquake event, while the others were successful. [PERSON] et al. [35] propose the architecture of an EW system that uses the 5G network to achieve low latency in transmitting data from a Structural Health Monitoring WSN to a server for data processing. By providing certain services with dedicated resources (\"network slicing\"), the 5G New Radio is able to support URLLC services that allow devices to send data with delays below 1 ms and with high reliability. Software Defined Networking, Network Function Virtualization and Mobile Edge Computing further enhance performance by being able to allocate resources dynamically to each service and deploy computational resources nearer to the end users. [PERSON] et al. [70] also developed an Earthquake EW system based on SHM, but with a focus on energy efficiency, which remains a key constraint in Earthquake EW, too. A sentry node was integrated into the gateway unit of a WSN that used the IEEE 802.15.4 standard. The sentry node is composed of a P-wave detector, a Wake-on Radio (WoR) transmitter, and a data sink radio. The WoR devices mounted on each node monitor the channel for wake-up signals, which are used to reduce the energy consumption in Rendezvous phases, i.e., when a receiver must wake-up when a transmitting node on a higher layer initiates a communication. The use of WoR devices allows the main processor of each node to go completely into sleep when no transmission is required.