A tsunami struck beaches around Sunda Strait in Indonesia on Saturday night, leaving dozens dead. What causes a tsunami? Where do these seismic sea waves mainly occur? Subscribe to us on YouTube: https://goo.gl/lP12gA Download our APP on Apple Store (iOS): https://itunes.apple.com/us/app/cctvnews-app/id922456579?l=zh&ls=1&mt=8 Download our APP on Google Play (Android): https://play.google.com/store/apps/details?id=com.imib.cctv Follow us on: Website: https://www.cgtn.com/ Facebook: https://www.facebook.com/ChinaGlobalTVNetwork/ Instagram: https://www.instagram.com/cgtn/?hl=zh-cn Twitter: https://twitter.com/CGTNOfficial Pinterest: https://www.pinterest.com/CGTNOfficial/ Tumblr: http://cctvnews.tumblr.com/ Weibo: http://weibo.com/cctvnewsbeijing