ping-animation.css

.pulse-button span:after{
    content: '';
    width: 30px; height: 30px;
    border-radius: 100%;
    border: 6px solid #673a9b;
    position: absolute;
    z-index: -1;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    animation: ring 1.5s infinite;
}

@keyframes ring {
    0% {
        width: 30px;
        height: 30px;
        opacity: 1;
    }
    100% {
        width: 200px;
        height: 200px;
        opacity: 0;
    }
}